thinking about fedi migration; it's better than it used to be because you can migrate followers and stuff, but my feeling is that there's a lot of people who hold off on migrating because it doesn't move your posting history and they end up staying on a server that reeeeally isn't a great choice (*cough* mastodon.social)

doing full-history moves "for real" in a comprehensive way is technically challenging; existing threads (which are spread all across the fediverse) would need to know about the new location of every post and swap it in; I can understand why this hasn't been implemented

BUT I don't see a reason why you couldn't have a copy of your old posts imported into your new account!

so I did that: https://git.sr.ht/~technomancy/masto-gear-solid

One of the biggest problems we had with post migration over ActivityPub is that if you change the id, your followers will see duplicates of everything you ever posted. If you don't change the id, they can't fetch it if the first site goes down. There's a solution for that now in FEP-ef61, so you can migrate and clone posts as easily over ActivityPub as we used to over Zot6/Nomad; where we created an overlay network to completely separate DNS from identity.

Files have their own set of problems. We give every member an integrated media library running on WebDAV. But sending a directory full of videos between servers is usually going to kill one of them due to various memory constraints. So I ended up creating a client-side plugin to stream a file at a time until you eventually get them all.

@mikedev right, if you relax the constraints and allow for solutions that involve implementor buy-in you can do a lot more, but my own experimentation is scoped to just what one instance admin could do on their own

because even beyond the implementation difficulty, just getting implementors to agree upon the solution is a tremendous amount of work

it's good work and needs to happen, but it's a very long-term process

Agreed. I've been working on it for a long time and against successive waves of opposition. Have something that works, though it all tends to fall apart if you need to do this across platform. I think the Misskey folks accomplished this using different ids, but they were only doing a one-time migration aka "account move", so didn't need to worry too much about duplicates. We're doing account copy/clone and both the identities and all their content are available simultaneously on multiple instances. In this case they all need the same portable-id or the whole thing quickly becomes a nightmare. But for what you're doing, I would encourage you to have a look at Misskey's migration tools for inspiration.