Signal's "source available" infra can be self-hosted but it's huge effort and relies on a bunch of cloud-specific services which need to be replaced with self-hostslable alternatives. It's also extremely poorly documented and the code quality is fairly mediocre. I wouldn't recommend trying to host Signal infra yourself; it can be done; I've done it at work and it took some months of effort, and maintaining it is a nightmare (or was, then at least) because they'd only push one huge update to GitHub quarterly or less often.
I've heard WhatsApp recommended from people I trust, but I have never personally used it so can't speak from experience.
Your suggested alternatives are owned by Zoom and Facebook. I'll stick with Signal.
All of them being tied to a phone number is bad form.
> Crypto thing they attempted
well...