The was of nomadic identity
Hubzilla was the first application to show us the concept of nomadic identity. It proove the concept that you can use many servers with the same account or moving your fediverse account from server to server. At that time the protocole was zot.
Mike MacGirven continue the work with an other application : Streams He implemented that concept with the popupar protocol ActivityPub. You can real more technical explaination here
https://codeberg.org/fediverse/fep/src/branch/main/fep/ef61/fep-ef61.md