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 didn't write the quoted list, just helped the OP with his formatting. I use proton drive, not dropbox.
I had no idea Proton Drive was a thing. I'll switch to it, Dropbox is becoming incredibly obnoxious with the advertising popups and notifications.