Edit: I’m glad so many of you have had no issues with multiple monitors. My set up is a little unusual (3rd display is an infrequently used large tv hooked through the receiver) and is definitely solveable but will take some effort (and honestly, I’d rather spend my spare time outside or with friends, so who knows when I’ll fix it.)
I have problems to this day with a single monitor setup. When I switch the monitor to another input (e.g. to play with my Switch), KDE Plasma, X, or something else freaks out, about half the time (I’m guessing it has something to do with locking or DPMS timers). When I switch back, it is running that the “safe” 640x480 which can’t display enough of the display settings panel under system settings for me to restore the 1920x1200 monitor native resolution!
Things are better than 2007, and they might be better than MS Windows, but “no trouble” is inconsistent with my experience.