Overview page: https://www.gog.com/en/anniversary
Direct sign up for Galaxy Linux beta: https://www.smartsurvey.co.uk/t/YEF5EV/
Not ever too late. They offer a lot of good products for dirt cheap. Don't give up on Gog just because everyone is on the steam dick (myself included). The best part is you own your game from GOG. They give you full offline never online installers for all the games on here.