Like the last patch we got a couple of days ago was 2.2.6, which is beta, instead of 2.2.5. Is this just me? I don't remember ever doing anything on Galaxy like switching on betas.
Normally GOG users don't receive beta patches since, as you note, there is no such option in Galaxy to opt in. However, Stellaris recently had an absolutely botched patch in the 2.2 release that basically rendered the game unplayable, so when the beta patch became available for Steam users someone made the decision to distribute it to GOG users. Since we don't have the option to opt in or opt out, the decision was made to opt us all in as the lesser of two evils. We've been on the beta patches ever since then.