Almost all. Either not possible or not useful. Telegram has huge public community. People need to be able to join/leave and forward stuff to other places etc. etc. It just makes no sense to add any e2ee to that. Even in normal groups the default is that any user can add someone so the new user would need to get the decryption key on invite. Then you have bots that need to be able to read messages so they need the key too. Then you have cloud search so telegram itself need the key as well. Its just completely nonsensical at that point even if it somehow would be possible to implement it.
>They absolutely did not.
https://telegram.org/faq#q-why-not-just-make-all-chats-39sec... I have no trouble understanding it. You may not like it but its clear and easy to understand.
>Which feature isn't being copied?
All the ones that are not possible with e2ee.
>Signal just implemented effin stickers with end-to-end encryption.
Yes, and its an anti-feature for most people. People dont care if a sticker is e2e encrypted send to a chat. But what user care about is how fast it is, how much data it uses and how much it drains the battery. Telegram easily wins all of this because it does not e2e encrypt stickers, instead they are stored in the telegram cloud and the message only contains a file_id for the other user to load the sticker (once, then it is cached locally)
>Firstly, new users in e.g. Signal groups don't get access to group message history.
More anti-features, normal user want a new user in chat to be able to read the history. (If not telegram allows it to be disabled)
>overwhelming majority of Signal groups are not public.
How is that relevant. Use cases are different. I use telegram almost exclusively for public stuff or semi-public stuff. Maybe this is the problem here. You dont use telegram and dont know that it is way more than a messenger. Its more like a social media platform.
"I dont want or use any of that (you, probably?)" Fine, stick with what you use but dont tell me everything telegram does could/should be done with e2ee. Its absurd and nonsensical. It would be like making twitter completely e2ee rather than just give the user and secure e2ee DM option. Which is what telegram did. You have the option for e2ee one-on-one chats if you actually need it. Ive used it a few time like to send someone a password or a private document. But for the most part I have no use for it.