Good morning Fediverse.
Portable identity for the Fediverse is another of these issue conflations that need to disappear from the Fediverse. Basically, Fediverse software already conflates a lot of stuff. They provide you with an identifier, they provide a public profile, they manage storage, they syndicate your posts, and many other things. Portable identity now takes this entangled mess and demands you can transfer it LOL
The correct approach would be to untangle the mess. For example separate out the identifier management from the Fediverse software. I've written a proposal to prototype fund in the late fall, so maybe there will be news on this by the end of the year.