I am just a bit concerned about their attitude. If they were to release a decent open source Linux client with compatibility layers (just free ride Valve for now...) and commit to maintaining it, then I guess I am on the boat. Last time I checked the process was not very polished and games could be outdated.
Steam (via Proton) generally works, though, for those who wish to use it. (Steam+Proton also works with things downloaded from outside of Steam, too, and has for years[0].)
Proton itself is open-source[1].
If someone wanted to package up standalone Proton binaries for a Linux distro, then I don't see any particular barriers that would prevent that.
On GoG's part, they do provide the ability to just download a game with a web browser (the old-fashioned, DRM-free way). From there, I can manage the games I that own in any way that I choose.
Thus, I'm simply not seeing a problem here that needs solved. I already have the freedom to do whatever I want.
Which part of this situation is broken, do you suppose, and why does GoG in particular need to fix it?
[0]: https://boilingsteam.com/valve-breaks-the-shackles-of-proton...
[1]: https://github.com/ValveSoftware/Proton