End-to-End Encryption is good but metadata protection counts as much. Names, group descriptions and memberships, avatars, who talks to whom ...

Both #deltachat and #signal go to great length to protect all the metadata that WhatsApp grants itself gratuitously. #Matrix stores similar scales of metadata on their servers, even if you can choose which server stores it.

Everything is better than #Telegram which additionally stores message contents in all group chats/channels and most 1:1 chats.