Omarchy happily grabbed an IP address after the Debian-to-Omarchy switch, but DNS queries skipped my Pi-hole and went straight to the public internet. In my case, the split-DNS setup for my homelab did no longer work either.

Symptom

resolvectl status shows the NIC using the correct settings from DHCP, yet a global block still wins:

Global
           Protocols: +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
    resolv.conf mode: foreign
  Current DNS Server: 1.1.1.1#cloudflare-dns.com
Fallback DNS Servers: 9.9.9.9#dns.quad9.net
                      [...]
          DNS Domain: ~.

Why it happens

On a fresh Omarchy install systemd-resolved is present but disabled. For a reason I didn't investigate, NetworkManager did never apply the DHCP DNS settings announced by my LAN.

Fix it

1. Point /etc/resolv.conf at the stub resolver and start systemd-resolved.

   sudo ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
   sudo systemctl enable --now systemd-resolved

2. Release and renew the lease so NetworkManager re-reads the DNS options.

   sudo dhclient -r && sudo dhclient