Thanks for the tip about SimpleX, that looks interesting! I could never use Signal due to the way they operate and force you to rely on their and Google’s servers, actively blocking forks from their network. So much for FOSS…

You should still go for it though! You can contact people on radio, you don’t need to necessarily have anyone local join you to achieve that. At most times of the day, there are hundreds of radio contacts being made. Now actually receiving those, and reaching those stations yourself as well in order to make a contact, that’s the challenge. And there are many different ways to achieve that with different gear on different frequencies in all sorts of different conditions. You can do much more than just a bit higher power walkie-talkie, you can reach the other side of the world if you go at it well :).