A non-recoverable account would be an account with no recovery phone number that can receive SMS codes and no recovery email. I will emphasize again that this is a really risky way to set up a Google account.
Another problem is that there's no guarantee that Google will not at some point require all accounts to be recoverable.
This development just makes it all the more obvious that this workaround of using a non-2FA Google account is just a bad idea and you should probably be doing something else instead, like running Channels on Docker.
Edit: and I had forgotten that you still need to have a 2FA-less account with Google for authentication to work, even if you're running Channels on Docker, so I was wrong about that part.