It depends on the client and the security implementations they support. For example IIRC no client support the last version of OMEMO (I think it was about OMEMO, I remember an article about it some time ago). Also are you sure that all the other people’s clients are on the same version and you’re not susceptible to a downgrade attack?
Unless you are ready to/want to control the whole environment (i.e. at least the clients and possibly the server), look into simplex.chat
Nothing is safe short of self hosted matrix with full E2E encryption or similar and ain’t nobody doing that.
Well, I’m doing that. But I’m nobody, so I guess your point still stands 😅
But also, I don’t judge the chats mainly by their client, but the protocol. Telegram is not open and so can’t be audited properly, that’s my concern.
Selfhosted gotify rules