While it would be great to see official support, the Heroic Games Launcher is a very good way to play GOG (as well as Epic and Amazon Prime) games on Linux.
Since last update, 2.13 I think, it does not work well with gog games, at least was not able to install flatout and pillars of eternity, both from my gog library. Nonetheless I was able to install pillars from the epic store, using heroic. With flatout I spent a week trying to debug installation problem, clear cache, reinstall of heroic, and everything else and then simply used lutris which installed flatout at first try and let me play right away (steam deck)
If only that were a long term solution. Heroic works for me on average for a week and then fails to connect to game stores and even forgets where the games are installed sometimes.
It fails on my laptop and my steamdeck. I love when it works but it’s not consistent.