* Messages are cleartext w.r.t. the server by default (I'd wager >99.9% of all Telegram chats are sent this way). E2E-encrypted conversations have to be enabled explicitly, are tied to a single device and only available on mobile.
* Encrypted group-chat not possible.
Hell, you might as well use Google or Facebook, the only difference is who's monitoring. Even WhatsApp has more privacy than Telegram.
Of what I tried so far, Keybase is really damn close. Their UX has been improving a lot, multi-device where all are first-class citizens, E2E by default, etc etc. The whole identity-graph thing, server-side being closed source and platform being run by a US-based business are the only things that keep me from trying to onboard everyone I keep in regular touch with. Too bad neither of those things are likely to change anytime soon.