Dns test 443
From AAISP Support Site
DoH
If you entered http://encrypted-dns-tester.aa.net.uk in to your browser and landed on this page, then your DNS lookup was via DoH and you reach this page using IPv6.
If you entered http://encrypted-dns-tester.aa.net.uk in to your browser and landed on this page, then your DNS lookup was via DoH and you reach this page using IPv6.