I would say the bare minimum is supporting their game client on Linux. They don't need to be supporting project developments like Valve, but at least giving a token gesture that they recognize and are doing their part for this issue would be a nice gesture to the gamers who feel that anti-DRM/game preservation and a future with Linux are very correlated - regardless of Linux's present-day state. By not having their game client available on Linux they have actively hindered the growth of Linux, and only through Valve's support are we getting closer to that future (as well as the Linux community who have eventually made their own GOG clients due to the lack of official support).

They have been making a willful choice to not use any of their money to support Linux, which has been clear for many years by the GOG users overwhelmingly asking for Linux support to no avail. Their Linux game installers are the bare minimum of using someone else's setup installer. I'm saying that if I'm going to be giving money to somebody, I'd rather give it to a company that's doing more with it and seems to have a stronger belief in actually making the effort to achieve this future instead of waiting for it to happen by someone else's hand.

Isn't GOG part of CD Projekt? Not a behemoth like Valve, but not a small fish either.