Long story short, I wanted to be able to access various things on my home LAN while not at home (mainly my Home Assistant instance). I enabled OpenVPN on my Untangle instance, and followed the setup ...
10.0.0.1 - Asus router - DHCP set up for 10.0.0.0/21 subnet (10.0.01 - 10.0.7.254). 10.0.1.1 - primary pihole for adblocking 10.0.1.2 - secondary/HA pihole 10.0.1.3 - PiVPN running on an RPi 4 / ...