[zeehio]

The closest solution I remember to this happened roughly 15 years ago when there was a browser extension that detected pgp on Email bodies and was able to get public keys and encrypt/decrypt emails automatically or with a single click, if I recall correctly.

It felt a small team or a single person project. There was a cat and mouse game being played against Gmail interface changes, with the encryption being broken every now and then. It required me, a random user, to trust the extension developer(s) with my Gmail and gpg keys. I had fear of having an xz backdoor situation compromising my Gmail account and gpg keys.

And for this extension to succeed I also had to convince all my Gmail friends and contacts to use it, and convincing them to trust the developers of the extension as I had done.

While I felt confident that the extension was perfectly safe I didn't dare to convince my family and friends to use it because (a) I could not guarantee that the extension wouldn't be compromised in the future and (b) the chance of the extension being broken in the future due to a Gmail UI change was close to 100%. Also the more users the extension had the higher the chances for someone to attempt to infiltrate to attempt a backdoor...

If I recall correctly, eventually the developer got tired of the Gmail UI changes and increasing demands of users and moved on, stopping the development.

Anyone with time could try to develop such an extension, but there were drawbacks back in the day...