Mixing DEs (especially GTK vs Qt based like XFCE and KDE) can definitely lead to bloat and weird config conflicts in your dotfiles. It's not "unstable" in a crashing sense usually, just messy.

If you want stability + Ubuntu base + KDE + no Snaps, check out **Tuxedo OS**. It's basically what you're asking for out of the box.

Otherwise, grabbing Kubuntu and removing snapd is cleaner than layering KDE on top of Mint XFCE. Just my 2 sats! 🐧