Is it possible to move from another self hosted instance to this - and keep my myname@mydomain identity?
I see the documentation for the standard mastodon move functionality but I think that assumes you also change username. So steps, via a temp account and a delay, would work I guess.
Is there a way to use this functionality for moving followers (which is the only thing I'm concerned with...) from one server implementation to another (this one) whilst keeping the same identity?
Unfortunately, and as far as I know, the ActivityPub protocol does not provide a migration path for this case.
I think you could also have issues with go from domain A to B, and the change the software of domain A, as some servers are caching everything and won't support handling a different software on the same domain. On changing domains, I did re-set the microblog.pub instance with the v2 (and new keys), and it seems to still work, but I wasn't able to re-import followers.
So this is a bit tricky, I can try to do some more research if I have time, but right now I don't have an easy answer.