Signal is a privacy first app. Do I wish it would not use a telephone number? Absolutely! But they never claim to be anonymous. This said with something like https://juicysms.com you can register signal and many other services with a number in the USA, the Netherlands or the UK (the Netherlands is the best option here)
If you look for an app what don’t need a telephone number check simplex or session. Perhaps something like the matrix protocol and element would be a great option too.
Skiff is pretty good, I switched from proton over as they had a good one year promo and I found it fits better on what I need. The drive and page setup is pretty good too and so is the calendar. Overall I like skiff and they update and add a lot almost weekly. Big fan so far
Metager.org could also be a good daily drive
I have no Facebook or Instagram etc and never had. And I have friends and meet people. I think people who are interested in you have no problem with your stand even changing the username all the time is a bit strange haha