I’d go for Matrix, with Element or Schildichat (not the next gen versions for now) as clients. It’s federated, which means you can choose which instance you want your account to reside on, end to end encrypted, has (video) calls, and some other features you wouldn’t necessarily expect from others like spaces for groups with several group chats, prioritizing conversations (low, normal, high / favorite) and threads inside a conversation.

Sendergruppe deren Inhalte niemand schauen sollte verkauft altbackene Zeitschriftenformate die niemand lesen sollte an Verlagsgruppe von der niemand was kaufen sollte.