looking for half-stable Linux distro

Hello, i am currently looking for a Linux distribution with these criteria:

-it should be more or less stable, comparable to Ubuntu with or without LTS // -it should not be related to IBM to any way (so no fedora/redhat) // -it should not feature snaps (no Ubuntu or KDE neon) // -KDE plasma should be installable manually (best case even installed by default) // -no DIY Distros //

I've been thinking about using an immutable distro, but if anyone can recommend something to me, I'd be very grateful //

Edit: I'm sorry for the bad formatting, for some reason it doesn't register spaces