Bilbo

The quickest way is to add the Newpipe repo: https://newpipe.net/FAQ/tutorials/install-add-fdroid-repo/

If you already installed Newpipe from the f-droid main repo, you may need to backup your data, uninstall and reinstall it. https://github.com/TeamNewPipe/NewPipe?tab=readme-ov-file#installation-and-updates

You could boot on an USB, mount the filesystem and change the permissions. But if the dude changed a whole lot of permissions, reinstalling might be the smart thing to do…

Klipper on KDE offers a clipboard history. Don’t know about other DEs.

Not a great timing to move to something RHEL-based!

If I may ask, why not Debian? You’re already familiar with 99% of the distribution, as it’s the base for Ubuntu.