See Ignoring domain CONFIG_DOMAIN for DHCP host name HOSTNAME - #8 by DL6ER.
In your case, create /etc/dnsmasq.d/99-domains.conf and add:
domain=XXX.XXXXX.SE,<ip-address>,local
Substitute XXX.XXXXX.SE with your actual domain from the warning, and <ip-address> with the IP of your RS30139079 host.
Run pihole restartdns for those settings to take effect.