Meh, just run several associated services and keep the same username on all of them. Nothing is interoperable, stop trying to force it. And a rogue app with bad user data handling practices is still going to leak your data, even if you store your copy of the data securely.
My fediverse accounts are always “patrick@<service>.bestiver.se”. I currently am only running Mastodon/Lemmy and a few supporting services (e.g. a link manager - https://bestiver.se/@patrick), but I’m adding more as I get to them. Pixelfed, Peertube, Loops(?), Piefed…
Adopting this ActivityPods thing looks like it will require each Fediverse project to make what I’d guess are fairly significant changes to their user data handling, and none of those projects are properly funded for this. In fact what this actually seems to be doing is asking every other Fedi app to build on top of their user data API.
I applaud the attempt at building a new standard in the Fediverse, but I doubt it’s going to happen.
That’s cool. Personally I just integrated it into my normal chat client by connecting Aichat, which supports a ton of backends including Ollama and hosted options, with Matrix.
Blog post with more info https://jackson.dev/post/chaz/