I speak for my own experience but KDE has been incredibly stable on my machines. For work, I use Plasma on Debian Bookworm and after putting in some work to set Plasma up the right way (set up my favorite fonts, scaling factor, etc.), everything works without issues/crashes. On my personal machine, I'm using Fedora Kinoite (immutable Fedora with KDE) and the experience has been similarly splendid. I do feel that Kinoite is a bit more polished than Debian but I guess that has more to do with Debian's opinionated principles rather than anything else.