Hello, asking for help because I have a habbit of messing things up while experimenting.
I have experience with pi’s (and Linux) but this is the first time I use Dietpi.
At the moment I have a Pi4 running DietPi and the following:
Adguard Home
Unbound
Home Assistant (for the above and some home automation)
Tailgate (to access H.A. when away)
I also have NordVPN and would like to implement it too.
The Pi is not the best to run VPNs, if you can find a Rockpi it has AES accelerator.
You basically need to advertise the dietpi as gateway and dns in your network. USG must stop advertising itself apparently. That will cover goals 1 and 2.
For the 3rd you’ll need a policy routing rule to use USG as gateway for the traffic from HA.