andrej567 I had signal and trouble was that because some people had my phone number, they kept contacting me, like hey old pal how are you... I did not want to block them but at the same time i was not in mood to chat with them and kill time.
You should be able to use Signal and avoid this issue by setting "who can find me by phone number" to "nobody". Check phone number settings in Signal and set both of them to nobody. To the old pals this should look as if you weren't on Signal at all.
For the rest I agree with @N1b, that a good messenger is safe and privacy respecting and makes your peer groups available. In this sense, Signal might indeed be the best compromise. I still don't like that a phone number is mandatory to set up an account.
I also tried out Threema, which is nice if you have someone to message. I also like the idea, that it is a paid app and thus makes more clear, where the money comes from.
SimpleX looks promising and innovative, but I don't know anyone using it.
23Sha-ger so it's a good option to keep it in a separate Shelter profile registered on a prepaid sim.
As far as WA is concerned, this will hardly allow you to use it on a regular basis and stay anonymous, even with a VPN.