Cinnamon I’ve found to be buggy too. Panel and wallpaper glitches, black screens on wakeup, to name a few.

You’re making assumptions. I’ve used GNOME since 2008, with extensive use of KDE and Cinnamon too in later years. I’ve used other DEs such as XFCE for niche applications. KDE - for me - has always been buggy despite being the most feature rich. This is just my experience. You don’t have to trust me.

Edit: Currently daily driving COSMIC. It was a little rough in the Alpha stages but it’s now very stable for me.

Unfortunately, KDE is quantity over quality. I like the look and feel for the most part, but out of all the mainstream DEs, I’d say it’s the buggiest. GNOME with too many extensions is absolutely less stable, but vanilla KDE is embarrassing for stability, even on Linux Approved hardware.