Overview page: https://www.gog.com/en/anniversary
Direct sign up for Galaxy Linux beta: https://www.smartsurvey.co.uk/t/YEF5EV/
They'll like use the ULWGL–Unified Linux Wine Game Launcher for that. It's basically all the tech Bottles, Steam, Lutris, etc worked on thrown into one project to prevent duplication and share prefix stuff between launchers.
Edit: Whoops, I guess the project was renamed to UMU.