Basically nvidia shadowplay for linux
GOG has DRM for many titles: see Galaxy. As I understand it, it isn’t as pervasive as Steam, but is necessary if you want multiplayer on many titles or care about extras like achievements.
Cloud sync also requires the drm, but the advantage that gog and itch have over steam is that for most games you just get the executables and you’re good to go.
Tbf to cloud sync, nothing is stopping you from using your own backup/restore service with your drm-free titles compared to the other features that Galaxy offers.
Achievements or multiplayer matching not being implemented in the game itself isn’t on GOG. They still allow you to download and launch any game you’ve bought, without even requiring galaxy.
Also lesser known is the fact that there are DRM-free games on steam. Download them once, you can play without having steam running or even installed. Using a client to download isn’t inherently DRM either.
