I am becoming increasingly doubtful of #Telegram's background and direction. #WhatsApp is owned by #Meta and just announced that it will introduce ads. So, it looks like I'm left with #Signal and #Matrix. The former has a better UI, but it's centralized and US-based. The latter is a bit clumsy but decentralized and EU-based. Neither is perfect, but they are the closest to it for me.
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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.