I think the main issue here is the mindset of "installing a new distro will fix it". Unfortunately, a lot of people online push that idea. If it's broken on Mint and Bazzite, it's probably a generic Linux issue.
The second issue with Plasma sounds like it could be related to Wayland and fractional scaling.
Barrier has been unmaintained for a while now. The two active forks are deskflow (upstream) and input-leap. Deskflow has limited supported for Wayland. It seems that they're working on resolving the remaining issues: https://github.com/deskflow/deskflow/discussions/7499