Clean up Gnome Desktop to accept Gnome shell extensions

Something has happened with my Gnome desktop - the previous Gnome shell extensions like Dash to panel have disappeared and cannot be reinstalled.
Just get a basic Gnome desktop. And the login screen selection menu doesn’t seem to contain the previous ‘Gnome on Xorg’.
(On the hardware forum I also have requested how to replace the Nvidia driver with Nouveau)

Is there a way to reinstall a clean Gnome desktop on my existing /home file system, except remove and reinstall the Gnome desktop pattern?

gnome-shell --version
GNOME Shell 3.34.5

zypper lr
Repository priorities in effect:                                                    (See 'zypper lr -P' for details)
      90 (raised priority)  :  1 repository
      99 (default priority) : 10 repositories

#  | Alias                                        | Name                                                         | Enabled | GPG Check | Refresh
---+----------------------------------------------+--------------------------------------------------------------+---------+-----------+--------
 1 | download.nvidia.com-$releasever              | nVidia Graphics Drivers                                      | Yes     | (r ) Yes  | Yes
 2 | ftp.gwdg.de-openSUSE_Leap_$releasever        | Packman Repository                                           | Yes     | (r ) Yes  | Yes
 3 | google-chrome                                | google-chrome                                                | Yes     | (r ) Yes  | Yes
 4 | opensuse-guide.org-openSUSE_Leap_$releasever | Libdvdcss Repository                                         | Yes     | (r ) Yes  | Yes
 5 | packman                                      | Packman                                                      | Yes     | (r ) Yes  | Yes
 6 | repo-backports-update                        | Update repository of openSUSE Backports                      | Yes     | (r ) Yes  | Yes
 7 | repo-non-oss                                 | Non-OSS Repository                                           | Yes     | (r ) Yes  | Yes
 8 | repo-oss                                     | Main Repository                                              | Yes     | (r ) Yes  | Yes
 9 | repo-sle-update                              | Update repository with updates from SUSE Linux Enterprise 15 | Yes     | (r ) Yes  | Yes
10 | repo-update                                  | Hovedpakkebrønn for oppdateringer                            | Yes     | (r ) Yes  | Yes
11 | repo-update-non-oss                          | Oppdateringspakkebrønn (ikke åpen kildekode)                 | Yes     | (r ) Yes  | Yes

inxi -Fz
System:    Kernel: 5.3.18-59.37-default x86_64 bits: 64 Desktop: Gnome 3.34.5 Distro: openSUSE Leap 15.3 
Machine:   Type: Desktop System: MSI product: MS-7971 v: 1.0 serial: N/A 
           Mobo: MSI model: Z170-A PRO (MS-7971) v: 1.0 serial: <filter> UEFI: American Megatrends v: 1.K0 date: 07/10/2018 
CPU:       Topology: Quad Core model: Intel Core i7-6700K bits: 64 type: MT MCP L2 cache: 8192 KiB 
           Speed: 800 MHz min/max: 800/4200 MHz Core speeds (MHz): 1: 801 2: 800 3: 800 4: 801 5: 800 6: 800 7: 800 8: 800 
Graphics:  Device-1: NVIDIA GK208B [GeForce GT 730] driver: nvidia v: 470.86 
           Display: server: X.org 1.20.3 driver: nvidia unloaded: fbdev,modesetting,vesa resolution: <xdpyinfo missing> 
           OpenGL: renderer: NVIDIA GeForce GT 730/PCIe/SSE2 v: 4.6.0 NVIDIA 470.86