maybe a vpn provider that uses openvpn? advanced setup but you can have an openvpn client auto connect on boot and bind the mail and ddclient to the tunnel interface.
cloudflare has good support for ddclient, so when your IP changes updates are automatic.
what about that doesn’t work? just because you don’t know how doesn’t mean not possible.
https://developers.cloudflare.com/dns/manage-dns-records/how-to/managing-dynamic-ip-addresses/
https://github.com/ddclient/ddclient#using-ddclient-with-dhcpcd
https://openvpn.net/community-resources/configuring-openvpn-to-run-automatically-on-system-startup/