I guess depends what you consider DRM, some games appear to have problems

https://www.gog.com/wishlist/site/label_the_games_that_have_...

Last I checked, there is loads of DRM on GOG and most of the games that have it, force you to use Galaxy.

And we have always been at war with Eurasia.

Yet the standalone offline installed games won't run without libgalaxy.dylib (Mac) or Galaxy64.dll (Windows) which is responsible for outbound connections to https://galaxy-log.gog.com and https://insights-collector.gog.com?

To be clear: if you buy Disco Elysium on GOG, download the "offline game installer" without using Galaxy, install it, and run the game on a desert island, it will work (the network requests fail open). But if you try to run the game after removing the bundled dylib/DLL, it will not.

Why do Galaxy-free games ship with a mandatory dependency on Galaxy?

Famously so. The main method of deployment was an offline installer before they made Galaxy, and AFAIK Galaxy just downloads and runs the installer.