celluloid, pix, hexchat, hypnotix, rhythmbox, LibreOffice

Those applications uninstalled just fine without any dependency issues last time I tried Mint.

If you’re unsure, make a snapshot of your current VM state (if your VM software supports it). Then just uninstall the junk you don’t need until Mint breaks. Restore snapshot, test some more, and so on. Those on real hardware should use Timeshift to create snapshots.

Tip: Run sudo apt autoremove package in the terminal so you can see which dependencies that are removed.

You shouldn’t have to install any flatpak dependency manually. Flatpak should handle it for you automatically when you install your programs. (In most cases.)

I think I also had this issue using Cinnamon once, but then I just used VLC instead. Never bothered to look into why. Worked fine in GNOME for me though.

I found a thread with a similar issue: https://forums.opensuse.org/t/flatpak-mpv-broken-since-20240306-snapshot/172981

There it seems the issue was audio. Try running the flatpak version with flatpak run io.mpv.Mpv --ao=pulse path-to-your-media-file

Mint is known to use old software in its repositories as it’s based on Ubuntu LTS. The flatpak mpv should work though. flatpak install flathub io.mpv.Mpv and then run it with flatpak run io.mpv.Mpv https://www.youtube.com/watch?v=dQw4w9WgXcQ

If you don’t want to type flatpak run io.mpv.Mpv all the time, you can create an alias in your ~/.bashrc file. For example: alias play='flatpak run io.mpv.Mpv'. (After editing your bashrc file, run: source ~/.bashrc to activate the change). Then you can run it with play https://www.youtube.com/watch?v=dQw4w9WgXcQ.

Your mpv or vlc versions may be too old. Try updating them to the latest versions.