How to get Pi-hole to serve both wired and wireless network interfaces?

Bridge the suckers into one IP (pointers below in second part of my posting):

EDIT: Ow ps, IP 127.0.0.1 in below line (dhcpcd.conf) isnt necessary anymore:

static domain_name_servers=127.0.0.1

You can put any external DNS server IP's on that line.