In short - it’s working now; but could have been smoother…
Similar to issues posted with headless Mac installs - you appear to need to remote connect to complete the configuration; and I saw a ‘corrupt install’ popup at one point…
Maybe if you are running a headless configuration the assumption is that you know what you’re doing - but this has the potential to confuse people no end.
It wasn’t as seamless as the release notes suggest it should be anyway… 
Hi, @AndyR, thank you for the report. Our team is looking into the Corrupt build error when updating.
Thanks!
–
Ivan
Thanks.
In case it’s significant, I think the sequence was…
Roon Server running on W10 NUC, Roon running as remote on W10 laptop; did not select update all, but initiated update of both in quick succession; appeared to download and update; auto restarted, ‘update available’ flagged again; this time I clicked update all; appeared to be updating, but Roon closed and did not restart; manual start, could not find Core; remote to NUC, taskbar popup said ‘corrupt build’ (or similar… ); clicked ‘quit’, followed by a manual start; Roon GUI appeared and asked should this be Server (or similar… ), Confirmed; shut down GUI; returned to laptop and restarted Roon (as remote); now apparently working.
Still working - using android phone or iPad as remote - not had the courage to reboot the NUC yet… 