Recently, Home-Assistant have changed their stance, and only "support" installations on HassOS and Debian 10 (at the time of writing this).
Normally, this wouldn't really matter to me, as I don't really care about having a "supported" system or not. However, they also decided, that unsupported installations can't get OTA Updates through Supervisor, such as upgrading to the recently recently released version 2020.12.
Now, being curious as I am, decided to snoop a bit in the supervisor Source to find how this check works.
In the file
operating_system.py, on line 8, they check against the static string
Debian GNU/Linux 10 (buster).
The current value for this check is retrieved here, in Line 98. From the name of the variable we can see, that DBus is used to get the value.
After some more research, I found this, which states that
OperatingSystemPrettyName, OperatingSystemCPEName, and HomeURL expose the PRETTY_NAME=, CPE_NAME= and HOME_URL= fields from os-release(5).
Looking further, I found that
os-release simply takes the value from /etc/os-release.
This makes the check quite easy to bypass.
Doing this will obviously make your install unsupported. If you run into any issues during/after this modification, I take no responsibility in the matter.
On your Home-Assistant VM, simply edit
/etc/os-release, and comment out the existing
#PRETTY_NAME="Ubuntu 20.04.1 LTS"
and add the value Supervisor is expecting:
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
Afterwards, save the file and reboot the VM. Now you should be able to upgrade Home-Assistant through Supervisor again.