Earlier quoted context omitted.
Theoretically, couldn't the client send the message to one server and the keys to a different set of servers? Clients would request the encrypted messages from one server and the keys from another? That would imply client-side encrypted cloud backups, with external key management which isn't the case in Telegram, if it were it could be shown from client-side code. Also, even if that would be the case, it would just n…
I always took the claim of routing keys and messages in different jurisdiction to be about not writing them to storage in those jurisdiction, not about not having them in RAM. the idea being that there can be an internal policy to shut down the server and wipe the ram but it is harder to do with drives. I also have a question since you probably can answer: can E2E offer a similar user experience to what normal telegr…
There's no precedent I'm aware of that if e.g. NL Telegram server has the key in its RAM but not in its disk, that it doesn't have to hand out the keys. Also the keys and/or plaintexts can just be stolen by foreign intelligence establishments. It's not just judicial means we need to be concerned about. E.g., just because it's legal in China to hack Telegram servers abroad, doesn't mean it's right, and Telegram should take this into account.
"the idea being that there can be an internal policy to shut down the server and wipe the ram but it is harder to do with drives."
This is pure speculation and it wouldn't matter because key lifting attacks would be transparent, i.e. the exploit is polished enough not to raise alarms.
"I also have a question since you probably can answer: can E2E offer a similar user experience to what normal telegram chats offer?"
Yes. Except channels and extremely large supergroups. But these two don't enjoy expectation of privacy. You can't expect something you say to a group of 10,000+ people to remain private, people consider such groups public.
Encrpytion is just math so there's also no way around the UX problem of authentication that's part of E2EE, but since that's expected of users, it's not a problem either.
Everything else, group chats with roles, synced chats, file transfers, locations, stickers... you name it, can be done over E2EE, just look at how Signal is showing each of those can be done. It's not trivial of course, but like you asked, "can it be done", yes, it can.