I'd likely add the kubuntu-desktop
to your existing Ubuntu desktop, and select which you use at login, acknowledging that this causes bloat, can be confusing if not familiar with the programs etc (ie. costs involved). Most of my boxes have multiple desktops installed so I have no problem with this
Otherwise I'd suggest a re-install using "Something else" (using the ubiquity
installer used by Kubuntu, it's called "Manual Partitioning" with calamares
installer used by modern Lubuntu) and select your existing partitions but ensure you have format un-ticked.
This will cause
- your additional packages (programs) to be noted
- system directories to be erased
- system installed
- additional packages you had, re-installed (if available)
- no USER files are touched unless you selected format
This can be used to change releases (same release, skipping an upgrade, or to change desktop). Depending on what changes you had made the results are usually pretty good. (An example of an issue is if you caused a package of the prior desktop to be apt install -reinstall
and thus flagged that package as user installed (not as part of desktop); it will be remain present, but that change was user made..)