as a final comment, i noticed in the log that, following bootup, gdm fails then succeeds on restart:
Mar 08 09:25:04 xxxxxx.xxxxxxx dbus-daemon[1390]: [system] Activating via systemd: service name='org.freedesktop.Accounts' unit='accounts-daemon.service' requested by ':1.26' (uid=0 pid=2231 comm="/usr/sbin/gdm ")
Mar 08 09:25:04 xxxxxx.xxxxxxx systemd-logind[1521]: New session c1 of user gdm.
Mar 08 09:25:04 xxxxxx.xxxxxxx display-manager[2211]: Starting service gdm..done
Mar 08 09:25:04 xxxxxx.xxxxxxx systemd[1]: Started Session c1 of user gdm.
Mar 08 09:25:04 xxxxxx.xxxxxxx systemd[2266]: pam_unix(systemd-user:session): session opened for user gdm by (uid=0)
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm-launch-environment][2241]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (--) Log file renamed from "/var/lib/gdm/.local/share/xorg/Xorg.pid-2316.log" to "/var/lib/gdm/.local/share/xorg/Xorg.0.log"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X.Org X Server 1.20.3
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X Protocol Version 11, Revision 0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Build Operating System: openSUSE SUSE LINUX
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Current Operating System: Linux xxxxxx.xxxxxxx 4.12.14-lp151.28.36-default #1 SMP Fri Dec 6 13:50:27 UTC 2019 (8f4a495) x86_64
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.12.14-lp151.28.36-default root=UUID=15f1aa07-2575-4dab-9cd8-e0c391a89276 resume=/dev/disk/by-uuid/dedbef6e-c989-4075-a294-31f1b462264d splash=silent quiet showopts splash=silent resume=/dev/disk/by-label/swap mitigations=auto quiet
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Build Date: 18 January 2019 12:00:00PM
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]:
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Current version of pixman: 0.34.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Before reporting problems, check http://wiki.x.org
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: to make sure that you have the latest version.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Markers: (--) probed, (**) from config file, (==) default setting,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (++) from command line, (!!) notice, (II) informational,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Log file: "/var/lib/gdm/.local/share/xorg/Xorg.0.log", Time: Sun Mar 8 09:25:06 2020
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Using config file: "/etc/X11/xorg.conf"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Using config directory: "/etc/X11/xorg.conf.d"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Using system config directory "/usr/share/X11/xorg.conf.d"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) ServerLayout "Layout0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (**) |-->Screen "Screen0" (0)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (**) | |-->Monitor "Monitor0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (**) | |-->Device "Device0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (**) |-->Input Device "Keyboard0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (**) |-->Input Device "Mouse0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Automatically adding devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Automatically enabling devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Automatically adding GPU devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) Max clients allowed: 256, resource mask: 0x1fffff
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) The directory "/usr/share/fonts/misc/sgi" does not exist.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Entry deleted from font path.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) FontPath set to:
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/misc:unscaled,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/Type1/,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/100dpi:unscaled,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/75dpi:unscaled,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/ghostscript/,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/cyrillic:unscaled,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: /usr/share/fonts/truetype/,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: built-ins
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (==) ModulePath set to "/usr/lib64/xorg/modules"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) Ignoring unrecognized extension "XFree86-DGA"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) Hotplugging is on, devices using drivers 'kbd', 'mouse' or 'vmmouse' will be disabled.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) Disabling Keyboard0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) Disabling Mouse0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Loader magic: 0x558015af9d20
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Module ABI versions:
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X.Org ANSI C Emulation: 0.4
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X.Org Video Driver: 24.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X.Org XInput driver : 24.1
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: X.Org Server Extension : 10.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (++) using VT number 7
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE) systemd-logind: failed to get session: PID 2316 does not belong to any known session
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) xfree86: Adding drm device (/dev/dri/card0)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (--) PCI:*(1@0:0:0) 10de:1d01:1458:375d rev 161, Mem @ 0xfc000000/16777216, 0xc0000000/268435456, 0xd0000000/33554432, I/O @ 0x0000dc80/128, BIOS @ 0x????????/131072
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) LoadModule: "glx"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Loading /usr/lib64/xorg/modules/extensions/libglx.so
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Module glx: vendor="X.Org Foundation"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: compiled for 1.20.3, module version = 1.0.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: ABI class: X.Org Server Extension, version 10.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) LoadModule: "nvidia"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Loading /usr/lib64/xorg/modules/drivers/nvidia_drv.so
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) Module nvidia: vendor="NVIDIA Corporation"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: compiled for 1.6.99.901, module version = 1.0.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Module class: X.Org Video Driver
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) NVIDIA dlloader X Driver 440.59 Thu Jan 30 01:08:17 UTC 2020
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (II) NVIDIA Unified Driver for all Supported NVIDIA GPUs
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Fatal server error:
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE) xf86OpenConsole: Cannot open virtual console 7 (Permission denied)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Please consult the The X.Org Foundation support
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: at http://wiki.x.org
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: for help.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE) Please also check the log file at "/var/lib/gdm/.local/share/xorg/Xorg.0.log" for additional information.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: VGA Arbitration: Cannot restore default device.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) xf86CloseConsole: KDSETMODE failed: Bad file descriptor
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (WW) xf86CloseConsole: VT_GETMODE failed: Bad file descriptor
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: (EE) Server terminated with error (1). Closing log file.
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm-launch-environment][2241]: pam_unix(gdm-launch-environment:session): session closed for user gdm
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2314]: Unable to run X server
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm[2231]: Child process -2314 was already dead.
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm[2231]: Child process 2241 was already dead.
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm[2231]: Unable to kill session worker process
Mar 08 09:25:06 xxxxxx.xxxxxxx systemd-logind[1521]: New session c2 of user gdm.
Mar 08 09:25:06 xxxxxx.xxxxxxx systemd[1]: Started Session c2 of user gdm.
Mar 08 09:25:06 xxxxxx.xxxxxxx gdm-launch-environment][2319]: pam_unix(gdm-launch-environment:session): session opened for user gdm by (uid=0)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (--) Log file renamed from "/var/lib/gdm/.local/share/xorg/Xorg.pid-2327.log" to "/var/lib/gdm/.local/share/xorg/Xorg.0.log"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: X.Org X Server 1.20.3
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: X Protocol Version 11, Revision 0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Build Operating System: openSUSE SUSE LINUX
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Current Operating System: Linux xxxxxx.xxxxxxx 4.12.14-lp151.28.36-default #1 SMP Fri Dec 6 13:50:27 UTC 2019 (8f4a495) x86_64
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.12.14-lp151.28.36-default root=UUID=15f1aa07-2575-4dab-9cd8-e0c391a89276 resume=/dev/disk/by-uuid/dedbef6e-c989-4075-a294-31f1b462264d splash=silent quiet showopts splash=silent resume=/dev/disk/by-label/swap mitigations=auto quiet
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Build Date: 18 January 2019 12:00:00PM
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]:
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Current version of pixman: 0.34.0
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Before reporting problems, check http://wiki.x.org
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: to make sure that you have the latest version.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: Markers: (--) probed, (**) from config file, (==) default setting,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (++) from command line, (!!) notice, (II) informational,
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Log file: "/var/lib/gdm/.local/share/xorg/Xorg.0.log", Time: Sun Mar 8 09:25:06 2020
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Using config file: "/etc/X11/xorg.conf"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Using config directory: "/etc/X11/xorg.conf.d"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Using system config directory "/usr/share/X11/xorg.conf.d"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) ServerLayout "Layout0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (**) |-->Screen "Screen0" (0)
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (**) | |-->Monitor "Monitor0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (**) | |-->Device "Device0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (**) |-->Input Device "Keyboard0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (**) |-->Input Device "Mouse0"
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Automatically adding devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Automatically enabling devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Automatically adding GPU devices
Mar 08 09:25:06 xxxxxx.xxxxxxx /usr/lib/gdm/gdm-x-session[2322]: (==) Max clients allowed: 256, resource mask: 0x1fffff
...