Or ANproto https://anproto.com/ without the nostr baggage, what little there is.
Thank you for the reference to that project called anproto, never had heard of it and I'm still without understanding what problem it really solves. Seems to encrypt texts but then contains zero outside metadata to route it somewhere. The website is very scarce on details for someone unfamiliar the scuttle-something they mention.
There are dedicated profile notes which define which relays that account/identity prefers to send their messages but everything is flexible. It does forego much of the routing metadata, which in my opinion is an obstacle when you don't know which stations/relays are placed on a given geography but you want the message to "navigate" (sometimes quite literally) to a place/region.
For that type of things I'm a biased fan of https://xprs.dev because it bridges NOSTR identities/signing/encryption with APRS that can use store/forward and the routing follows any possible method include USB drives.
There's an example ANproto in use at https://wiredove.net it's pretty clean but not very active, yet another experimental social network playground!