welcome to the forum,
i do a similar thing but use tailscale.
that way insecure software such as minidlna and rclone serve dlna are not exposed to the open internet.
else can use wireguard, mullvad vpn or openvpn
fwiw, i have a howto guide
https://forum.rclone.org/t/rclone-on-termux-turn-your-android-phone-into-a-media-server/16064