For reference, here's what it looks like in a test environment I have:
dig +short SRV _dns._udp.resolver.service
10 100 5301 vm-dns01.
10 100 5301 vm-dns02.
vm-dns01 and vm-dns02 have an Unbound DNS server listening on port 5301 which can resolve toward the internet. Our unbound config looks something like https://unboundtest.com/conf