Not sure if it checks all your boxes, but you could have a look at the following (and tell us if they did) :

• https://heroicgameslauncher.com/
• https://github.com/kra-mo/cartridges

There is GameHub, but I don't think it checks all your boxes.

Pegasus frontend (I think, you'd need to look into it yourself) ticks all your boxes, and can be themed to look incredible but the setup process is highly involved.

Personally, I gave up on it. Seems like a great program so you might think it's worth the effort.

Part of the reason I gave up, I should say, is that I'm using my pc as a home theatre device as well as a games console. I went with kodi and advanced emulator launcher instead, which was similarly involved (I had to write very basic shell scripts for each game, apart from the emulated games) but the difference is I was already using kodi for my live tv and video streaming interface