Update – supervisor-2021.12.1 now available
The first release of December, 2021.12.1 update for the Supervisor is now available.
It’s not yet appeared on https://www.home-assistant.io/blog/ so it might have been pre-emptively released but my Dashboard was showing it is available.
One thing to note – on both my installations (test and my main installation) once completed it still showed an update was available, so if this happens to you, restarting should resolve this. In fact, I would always recommend restarting everything after an update, just to make sure any in-memory modules are unloaded and any config files are re-read.