Hi.
I am very interested in using this to connect a town where my cousin is in the mountains in spain with zero communication but want to use Briar messenger as it doesnt need server but i wonder if anybody has try it?.
Hi and welcome,
you are not alone with your request 
You can push this topic on Briar’s gitlab repo:
Seems like the Briar devs are not very interested, because the aren’t very familiar with the achievable range nor the use case.
Another thread for your information: