Update. I left the machine in this state for around an hour and it’s come online. Unsure what the issue was but hopefully it’s resolved. Will update if any further issues found.
I had a similar issue, except my server never started the update. Once I got to the select OS and Storage screen, it never started progressing. I restarted the server and since then I can’t find it’s IP address on my home network and it’s not restarting back to the normal homepage. I seem to have broken something. I did backup the server, but didn’t create a SSH key as I ran into issues there when trying to save a key.
Basically my server is unreachable now and I’m not sure how to recover it, even though I have a backup.
Have you tried running through the entire setup again? Since you have a backup from the originial migration process, this should be very possible. maybe try using a newer beta version, like beta.9