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
if i can’t use it in my already existing mail client it doesn’t exist to me
This. I’m much interested in Protonmail and Tuta, but until they can support SMTP / IMAP or have a publicly accessible bridge to operate with client-side mail, they’re absolute nonstarters for me.