I installed the Adguard appliance today out of interest to see how it performs. I think there are a number of improvements necessary here:
1: The documentation for installing it as a VM uses a simple multipass command. The problem with this is the resulting VM spins up on an isolated NAT which only the host can access, which is obviously not helpful for a DNS server. I get that your guide keeps it simple, and Multipass is excellent for this, but the end of the tutorial will leave some frustrated that it’s not working after following the instructions to the letter.
2: The guide should be much clearer that Adguard offers a paid service. As I ventured to their homepage searching for documentation I was immediately concerned that I would be asked for money after having already installed the software. This is a tone deaf oversight and not in keeping with the values I hold dear from Ubuntu.