You’re correct, that is the Supervisor version - 2020.12.7. My Home Assistant OS is 5.8, the dashboard states “You are currently running version 0.118.4”
So far any attempt to upgrade the Home Assistant Core to 2020.12.1 results in the error I noted in Update to 2020.12.1 failed.
Still waiting for suggestions on how to resolve.
Edit - Just tried again, same error
20-12-18 05:53:59 INFO (MainThread) [supervisor.homeassistant.core] Updating Home Assistant to version 2020.12.1
20-12-18 05:53:59 INFO (SyncWorker_1) [supervisor.docker.interface] Updating image homeassistant/qemux86-64-homeassistant:0.118.4 to homeassistant/qemux86-64-homeassistant:2020.12.1
20-12-18 05:53:59 INFO (SyncWorker_1) [supervisor.docker.interface] Downloading docker image homeassistant/qemux86-64-homeassistant with tag 2020.12.1.
20-12-18 05:54:14 ERROR (SyncWorker_1) [supervisor.docker.interface] Can't install homeassistant/qemux86-64-homeassistant:2020.12.1 -> 500 Server Error for http+docker://localhost/v1.40/images/create?tag=2020.12.1&fromImage=homeassistant%2Fqemux86-64-homeassistant: Internal Server Error ("Get "https://registry-1.docker.io/v2/": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)").
20-12-18 05:54:14 WARNING (MainThread) [supervisor.homeassistant.core] Updating Home Assistant image failed