Threema looks good, but as far as I understand, it's not completely open source and it collects some user data (as opposed to session). But yes... session still has quite a few bugs fix.
Discussion
Threema is open-source, you can also sign up anonymously, and it has perfect forward secrecy, which Session doesn't have.
Good to know. Thanks for clarifying 👍🏻 I thought that only the threema apps were open source. I'll have a closer look then, but I'm by all means not an opsec expert 😅 Any tips from the nostr community are much appreciated!