My ISP provide me with good IPv6 connection with support of opening ports how I like. But IPv4 is behind a CGNAT and makes me unable to host a service on the legacy Internet.

Unfortunetely some of my friends I want to host (Jellyfin and Nextcloud) for does not have modern Internet connection, so I have to put some proxy.

Now I need suggestions of a solution. VPN on some VPS they would need to connection to is one of them, but it should be as simple for them to use as possible.