Yeah, I mean migrating the software of a single-user instance, not migrating between instances, sorry if that was unclear.
So I currently run a single-user instance of Mastodon. Wondering if it's possible to start running a single-user instance of Pleroma instead, without having to change the username+domain?
My understanding is in theory yes. But in practice things might be more complicated.
Like merely keeping the same name and domain is easy enough. Just shut down the old system, start the new one, create an account with the same name. Of course you would need to refollow everyone. I'm not sure what happens to your followers. Your new server will not know they are followers, so unless this triggers mastodon to try to automatically refollow, I think they are left in a half-broken state. You definitely lose all your old content. All in all, this is not really a great option.
For a full migration where in theory everything works, you could try to follow the linked process to migrate to Pleroma 2.0.5, and then obviously just upgrade to latest following plemora documentation for upgrading. description of migration process: https://icyphox.sh/blog/mastodon-to-pleroma/ (This is based on the following migrator: https://gitlab.com/soapbox-pub/migrator). I have no idea if it works with newer mastodon minor releases.
So I currently run a single-user instance of Mastodon. Wondering if it's possible to start running a single-user instance of Pleroma instead, without having to change the username+domain?