I wonder how this might fit with the work done to extend easy account migration across the fediverse, with Portable Objects (FEP-ef61)?
https://codeberg.org/fediverse/fep/src/branch/main/fep/ef61/fep-ef61.md
The developer of Streams contributed a lot to this FEP, based on the NomadicIdentity features it's shared with Hubzilla for years(1). So it's already been implemented in Streams.
I'm curious to see it added to other ActivityPubs apps so I can test an app-to-app migration.