That convention does guarantee access to trade corridors for landlocked nations, though as the separatists do not want to join the UN I'd be interested in seeing how they think they'd benefit.

If you believe the APP's website they want to use the UN's 'Law of the Sea', but they also don't want to be a part of the UN cause they do not share values. So seemingly they think they can, they think they can.

The servers I suggested are much lighter and simpler to setup than synapse. Commet is very Discord like which lets you on board people much easier than Element. It also supports voice rooms unlike Cinny(waiting for this to merge https://github.com/cinnyapp/cinny/pull/2680)

Tuwunel or Contiuwuity for the server and Commet for the client(though presently you'll need to provide another client to register)