I don't remember exactly but essentially I read about zuckerberg and e2e and something along the lines of "before we encrypt the link or message, we would send a hash for verification and if passed, e2e would be go ahead and sent."

Dont remember if it was something to be done in future or existing tech because there was talks of misuse and this article had come.

I know if multiple Foss apps like Delta chat I think which uses existing infrastructure.