looks like rendering adblockers extensions obsolete with manifest-v3 was not enough so now they try to implement DRM into the browser giving the ability to any website to refuse traffic to you if you don’t run a complaint browser ( cough…firefox )
here is an article in hacker news since i’m sure they can explain this to you better than i.
and also some github docs
I moved to Fastmail a couple of months ago and it is fantastic. Much prefer it to Google Mail, besides the privacy improvements.