It's been going on for months. GOG standard operating procedure blame customer?
No other site on the net does it. As you can see all Addons are off except HTTPS Everywhere .

Also, why is the assumption the customer is not allowed to use any Safety protocol Addons?
Is the belief customers should be made, to be Security Vulnerable to visit GOG?

GOG is trying to protect itself and the customer, but why chose solutions that hurt the Customer?

This screenshot is AFTER, successful Two Step Login!

https://i.postimg.cc/02xV7ygY/GOG.jpg

...might be unique to you?

Not discrediting your problem (clearly there is one!) but I've never had an issue logging on or accessing GOG's pages. I have a lot of plugins active all the time; all to do with ad-blocking, privacy and security ('safety protocol addons'). And I haven't had this problem once?!

Hope you can sort it though.

... This add-on has always carried the risk of braking certain sites with "unexpected" insecure connections. While the developers admitted this openly they didn't explain the extent of this problem; whether it is a small insecure portion of the site or a major one which causes it, and whether or not the insecurity is addressed better using the browser's native HTTPS-only mode isn't clear.

We have no clue whether it's the site being insecure which has caused the add-on to nuke it (if it is the add-on at all). It may be the outdated add-on encountering a code block it didn't know how to handle properly.

Have problems too, like login take too long (it is more then year), maybe you shoudl get rid of google, Fb scripts! or create separate login . gog . com

also main page take forever loading, get rid of new stupid js libs and make it backward compatible

I'm the same, everything loads fine 99.9% of the time, except that GOG scripts no longer run quite like they should, such that the IN LIBRARY label often doesn't show, especially on the main (front) page, and some similar issues on other GOG pages.

I've put that issue down to two things, recent changes to the site by GOG (last few months) and my browser version, and perhaps my OS.

So unless the OP has something running on their PC causing a problem, I bet it is OS, Browser, Addons and or GOG changes related.