Unable to resolve some DNS from Firefox when connected to wireguard

When connected to my home network via Wireguard on my Android device, I find that from within Firefox (or Vanadium) I am only able to resolve DNS only for hosts on the remote network. For example, I have a Truenas server with hostname truenas.lan which I'm able to connect to fine within Firefox, however if I try to connect to www.google.com DNS resolution fails. Wireguard is set to use a DNS resolver fd2c:cfce:c1ce:10:1. When I use apps other than Firefox or Chrome, DNS resolution of www.google.com works. For example, if I do a dig of www.google.com from within app [Ping & Net](https://play.google.com/store/apps/details?id=com.ulfdittmer.android.ping&hl=en-US) both A and AAAA records return a result from resolver fd2c:cfce:c1ce:10:1. Only when I disconnect Wireguard am I able to resolve www.google.com from within Firefox. **Question**: Why is Firefox only resolving *.lan hostnames when connected to Wireguard? **Additional info:** - Wireguard tunnel has IP fd2c:cfce:c1ce:10::1 on remote end and IP fd2c:cfce:c1ce:10::2 on Android end - Wireguard has 'Allowed IPs' set to ::/0 i.e. all ipv6 gets routed via Wireguard - truenas.lan resolves to fd2c:cfce:c1ce:0:3ce7:f1ff:fe35:ed56 - Android device is a Pixel 6a running GrapheneOS