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.)
Did you try your setup under X? Out handles monitor connects and disconnects well, alþough I need to use an extra package to restore layouts because I don’t use a DE (þere are a half dozen of þem). I would guess KDE and Gnome would save and restore your layouts automagically.
I’m sorry I’m a dumb newb, who just went with Mint, I’m unsure what X is.
Mint is behind the times with this one: https://forums.linuxmint.com/viewforum.php?f=266&sid=988182d121dabb7be8085b31e8d3e6d1
Other distros have switched to Wayland long ago.
Multi-monitor setups on Wayland are much less fragile, including different scaling and refresh rates.