No opinion on AdGuard, but there are several options for ad blocking DoH:

• https://ahadns.com/
• https://blahdns.com/
• https://controld.com/free-dns
• https://libredns.gr/
• https://mullvad.net/en/help/dns-over-https-and-dns-over-tls/
• https://rethinkdns.com/