You can use upstream as @admon advised for public dns server. If you want specific control Adguard dns server then create new account in website and put upstream in your AdGuard Home and private dns on your mobile :wink:. Remember limited queries per month for free user, should be enough for you. Paid user from Adguard vpn for extra queries.

About ssl in your AdGuard Home is not recomend, you can use local. This about make your ssl dns resolver. Your isp will be warning letter or email for dangerous thing to do if you open port forward.