I'm not an expert on the specific of this, but changing the domain for the UI (as in oldsh.itjust.works) seems a lot easier than changing the domain for the backend, which includes federation with all other instances.
I don't know of any way to change the federated stuff without breaking pretty much everything and starting over.
Maybe there is and I just don't know about it, or maybe there could be an easier way at some point.
I'm not an expert on the specific of this, but changing the domain for the UI (as in oldsh.itjust.works) seems a lot easier than changing the domain for the backend, which includes federation with all other instances.
I don't know of any way to change the federated stuff without breaking pretty much everything and starting over.
Maybe there is and I just don't know about it, or maybe there could be an easier way at some point.