The Briar Project is an encrypted FOSS peer-to-peer messenger app which can be used online through @torproject or offline locally through wifi or bluetooth. The "not yet official" Fediverse account for Briar is at:
Its offline mode means it can be used locally even if the internet is shut down (for example due to disasters or other reasons).
Briar's website is at https://briarproject.org
This is a brand new server run by the main developers of the project as a spin-off of mastodon.social It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!