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've never been unable to access a site on Firefox due to DRM. There is a prompt asking to run DRM-enabled media, but that's it.
Edit: or is there something about Manifest v3 that will get Firefox blocked somehow? IDK how as I would think it would be easy to pretend to be compliant.
Click the Github link in the original post. Google has an RFC open right now about "web integrity" about ensuring users don't modify the content they see. They claim it's not to block plugins but... It's hard to think what else they could possibly be thinking of.