The safest way for remote-access to your game server would be hosting your own Wireguard server, and having people you trust VPN into your network.
If you really want to take it to another level you can then forward that VPN server through a VPN client essentially creating a multi-hop network, but you'll certainly see an increase in latency for everyone involved. The internet is your friend here, there are many ways to achieve this.
Edit: didn't realize how old this post was lmao
