This is true and I do apologize for having slipped up on this. I did a bit more research and came across this pretty decent read up on this github repo by Dessalines: why_not_signal.md that covers this issue in much better detail and provides alternatives. The only one I'm familiar with outside of Signal is Matrix which can be self hosted giving you a lot of leeway in protecting your own data and only requires you to use an email of which you can use a burner email to avoid connecting your identity to anything.