I installed Debian + KDE on my mom’s laptop. She hasn’t had a complaint since. How tech-savvy is she, you ask? I’m sitting with her right now, so out of politeness she put on headphones to watch her favorite soap opera. Mind you, the headphones weren’t plugged into the laptop. She was sitting there, headphones on her head, sound coming through the speakers, watching her soaps like this is how it’s meant to be done.
I’ve never used KDE before, how does it compare to Cinnamon?
Cinnamon is kinda like KDE with all the options removed.
KDE is whatever you want it to be. Out of the box it looks similar to Windows, but you can turn it into a tiling window manager, or a clone of Gnome, without touching the command line.
This sounds extremely impressive to me, as customizing Cinnamon without using overly technical tools has been quite hit and miss for me.
I like the Wayland support from KDE Plasma for things like HDR and Freesync. If you don’t need advanced stuff like that then it’s preference really, Cinnamon would probably be my second choice.