IN THEORY, any active pen device will work unless it's some crazy Bluetooth thing. Most of the more prominent makers use supported protocols (Wacom, MS, USI), but I'm sure there are some crazy cheap Amazon unknowns that use something else. Just stick to the major manufacturers, search what protocol they use, and if it's one of the major knowns, it'll work. How WELL it works is up to the pen and screen combination though.

Example: a pen may advertise 16k pressure sensitivity, or some tilt metric, but it may be that the screen will only be capable of X amount of capacitive touch. This shouldn't be a concern unless this screen is way old though. The pen does most of the advertised work for the input.

No idea but uBlue Aurora may be cool, try to rebase to it and see if you like it. It has a key input remapper included, and maybe a few more like solaar for LG stuff

I have the dell active pen on my xps 2 in 1, it works.

Linux has had MPP (Microsoft Pen Protocol) support baked in for some time now. Dell sells such a pen which they call the Dell Active Pen but theoretically any MPP pen should work.

For the love of god stop forcing people into Linux.