Oh wow! This has happened to me but never thought to look it up. Thanks for the link!

This one is a single flatpak that is self contained, the other one is a script that downloads the emulators one by one, in both cases you can pick and choose which ones you want to download from a list and they’ll do the rest if you provide the ROMs

I sometimes connect my steam deck to a computer screen with keyboard and mouse to play, yes.

I played it while connected to my screen, I seem to recall that in desktop mode, friends window, right click a friend and start steam play together, all while the the game is running.

I’ve played shredders revenge on my deck with 4 players via remote play together and had no issues whatsoever.

Each player was using he’s own controller to play. What was your problem exactly?

You have to use the Remote play together interface to map the player controllers to the local controllers 1 through 4, but that’s it.