One crucial thing I use my pihole for is to forward traffic going to the .lan top level domain to my reverse proxy (traefik), I couldn't figure out how to do this in the pihole UI so I just added a custom config file to /etc/dnsmasq.d which works perfectly.

I'm not sure what adguard uses but would be interested to here if it's possible!

EDIT: just seen it supports DNS rewrites, which seems to do a similar job. Nice! I might give this a shot for a while