I found an application called Alovoa through F-Droid, but I see you don't need an phone application to use it: https://f-droid.org/en/packages/com.alovoa.expo/ https://app.alovoa.com/ https://github.com/Alovoa/alovoa

Apparently data privacy and open-source is a feature, and it doesn't ask for a phone number.

Those I'm interested in are far away apparently, but I at least started a couple of conversations.