I like GOG a lot but it's wild to me that their GOG Galaxy client doesn't work on Linux! A lot of gamers who care about preservation and availability are spending money with Valve because Steam's DRM is mostly inoffensive and the Linux support is so good.
The addressable market segment of people who play PC games and also care about DRM-free accessibility would be larger if GOG's launcher ran on Linux and targeted Linux users. It seems like a logical overlap to me.
Valve is eating GOG's lunch in this segment but it could easily change. Sure it might be small but it's bigger than ever, still growing, and seems to fit GOG's mission.
I would definitely start repurchasing my Steam games DRM-free on GOG if only they provided a launcher with the tooling necessary to download & run them on my system.
As things stand now, and for all the good GOG does... it's not enough to be DRM-free but only distribute Windows installers. You've just outsourced the DRM scheme to Microsoft. If the software doesn't run on a DRM-free OS, the job is only halfway done.
And in the meantime, GOG's product is tragically subject to piracy, (I believe) partially enabled by their decision to _only_ package games for the OS upon which most piracy traditionally takes place! :( I hope this could be offset by packaging for a crowd with more ideological overlap.