[FabCH]

I don’t think there is a formal definition of E2EE.

Here’s Wikipedia’s definition:

„End-to-end encryption (E2EE) is a method of implementing a secure communication system where only the sender and intended recipient can read the messages“

Note the complete lack of client/server distinction. It’s simply about intended recipients.

[flossly]

In many cases "transport encryption" would also fit that definition.

E2ee is quite well established imho. The server at Hetzner (a.k.a. "someone else's computer") is NOT to be trusted in e2ee schemes. Until today I'd be willing to say everyone agrees on this, but now I doubt that :)