I wonder if there's a use case for "distributed but not to the global internet as a whole"?

Maybe you could have a Blueboat Docker container running in each office for local office/intranet users? Or one in each of the datacenters your users VPN into? Some simple-ish dns based geographical or subnet routing for a handful of Blueboat instances in your various on-prem or local cloud zones should be manageable enough without need ing too much magic.

Not sure how to sensibly sync them all or centralise databases/storage for them though.