Supervisor: blocked from execution, no host internet connection

Hello.
I have Ubuntu with installed HomeAssistant supervised. I know that Ubuntu is not supported by HA now. But I have it already for two years and I have got issues only a month ago.

Everything works fine except I can’t update any addon or install new addon or update HomeAssistant. I get this error:

22-06-20 07:19:40 WARNING (MainThread) [supervisor.jobs] 'AddonManager.update' blocked from execution, no host internet connection

I have internet connection on host system (Ubuntu). I have internet connection even inside the hassio_supervisor docker container (tested it by means of pinging google.com and other sites).
Maybe it’s something with DNS? I use Adguard Home. Maybe it returns wrong answers to the supervisor internet system check?

Also I have found this article about that: DNS server issues - Home Assistant
But I have analyzed the logs of AdGuard Home and responses for the _checkdns.home-assistant.io seems to be fine.

Here is the examples from the Adguard Home journal:

I also tried to restart supervisor service, restart supervisor container manually, restart host system.

Maybe the developers of supervisor can tell me how it checks the internet connection?