I just made my first purchases from GOG a few weeks ago, and did it from a Linux machine. I believe it auto-detected I’m on Linux and said “Hey, this game does not natively support Linux” right at the top of the game’s page, and even said “Hey, X games in your library dont natively support Linux” when I was at the checkout. As for the ones that did, it changed to saying “This game does support Linux” on the game’s store page.

Honestly, feels good to see this sorta stuff, but this is just each game on an individual basis, independent of GOG’s launcher.

Edit: Thankfully, throw in a smidgen of wine or proton, and it’s likely all the incompatibilities are compatible.