AdGuard Home supports static clients. Unless the instance is being used over TCP (port 53, unencrypted), it is by far the better way to use clientnames in the DNS server addresses and unblock the clients over that.

For DoT: clientname.dns.yourdomain.com
For DoH: https://dns.yourdomain.com/dns-query/clientname

A client, especially a mobile one, can simply not guarantee always having the same IP address.