use the wandns script to set your router upstream dns. It currently uses cloud flare dns but you can change the values to any dns u prefer.
That will keep your router upstream dns separate from AGH. It does mean your router won't use the AGH filtering but honestly should not be needed as you are only updating/checking rather than surfing from the router.
#!/bin/sh
# Reconfigure router DNS provider to cloudflare upstream
# Disable peer ISP DNS
uci set network.wan.peerdns="0"
uci set network.wan6.peerdns="0"
# Reconfigure router IPv4 DNS provider to cloudflare upstream
uci -q delete network.wan.dns
uci add_list network.wan.dns="1.1.1.1"
uci add_list network.wan.dns="1.0.0.1"
# Reconfigure router IPv6 DNS provider to cloudflare upstream
uci -q delete network.wan6.dns
uci add_list network.wan6.dns="2606:4700:4700::1111"
uci add_list network.wan6.dns="2606:4700:4700::1001"
# Save changes
uci commit network
# Restart network service to reflect changes
/etc/init.d/network restart
Other DNS providers