I’m not sure how that happened. Usually zypper gives clear conflict messages about removing software.
That was corrected and now I can select plasma5 when I login. But I want to have be the default choice whenever I start up or login.
Normally, you login to a DM screen (DM=displaymanager). Typically this is either SDDM or GDM. Both of those remember the destop selected for the most recent login, and it becomes the default for the next login.
With GDM, this is a per-person default. With SDDM, this is a default for all users (until somebody chooses a different desktop).
This will be a little bit more difficult – as nrickert mentioned, GNOME uses “gdm” as the Display Manager of choice; KDE Plasma uses “sddm” …
Once again with YaST – no Handbook for this – YaST section “System” – “/etc/sysconfig-Editor” – section “Desktop” → “Display manager”:
[INDENT=2]Value: “DISPLAYMANAGER” – set it to the value “sddm”, save and exit and then, reboot.[/INDENT]
Caveat: you have KDE Plasma components installed including, the Display Manager: sddm
Once you’ve returned to KDE Plasma as being your preferred Desktop environment, use the YaST Software Manager to clean up the GNOME bits and pieces which you don’t need.
Please be aware that, the Gtk environment is needed by default for applications such as Firefox and LibreOffice – therefore, even if your preferred Desktop is KDE Plasma, there are parts of the GNOME environment installed by default, to support the Gtk applications mentioned – please, please, read and understand everything
the YaST Software Manager pops up for you to review when removing bits and pieces of the GNOME Desktop environment …