I've not played much with the WAN on my USG, it seems to go.

I note the lack of DNS set here.

On my main lan network, the dns is set to 192.168.10.1, my usg.

I thought I'd put in the 2degrees dns server somewhere.

So when I look on the usg as the main dns I see:

show service dns
 forwarding {
     cache-size 10000
     except-interface pppoe2
     options ptr-record=1.10.168.192.in-addr.arpa,USG
     options all-servers
     options cname=unifi.guest.domain.unifi.ata.domain,unifi.iot.domain,unifi.domain,unifi.media.domain,unifi
     options resolv-file=/etc/ppp/resolv.conf
     options server=1.1.1.1
     options host-record=unifi,192.168.10.45
 }

So interesting, that's set to 1.1.1.1 cloudflare.  Is that where having nothing in the WAN config screen is defaulting to 1.1.1.1?

What brought me here was a lack of dns at all this morning until I restarted dnsmasq on the usb, and in the dnsmasq log I saw an errour about: could not find: /etc/ppp/resolv.conf as listed in the dns service.