Element does not require a phone number.
Neither does Telegram since last year: https://www.theverge.com/2022/12/7/23498236/telegram-fragment-phone-number-crypto-verification-monetization
Signal literally exists. Free.
Signal has fewer features than non-premium Telegram. Both are open source, neither can be used with alternative servers (unlike Matrix).
Vielleicht ist seine Kernkompetenz doch das Moderieren auf Pro7. 😂