TheFrommie86: I have gotten a reply on my Ticket on this Issue:
"Hello,
Thank you for your patience.
Our teams and developer are aware of missing update for GOG.COM version of the game and are currently working on proper version fitting GOG.COM needs.
Unfortunately, I do not have any ETA that I could provide at the moment."
To me it sounds they are working on a Solution to Implement the Golden Pistols so you don't need a 3rd Party account.
But that, I admit, is only speculation on my part
The problem is, answers like these have been gotten already by other users since weeks ago, but nothing came, not even when the new update to remove AI-licensed assets was pushed to other platforms
The Golden Pistols things is otherwise purely opt-in from what I can gather.
Even recent Bethesda titles like DOOM + DOOM II and the like require signing up an account to bethesda.net to access all features, and these have been published and updated with little to no delay, so there's no GOG-wide ban against third party services if they are opt-in only
Something happened is my guess