You could use OpenZiti instead. This replaces OpenZiti/ZeroTier, implements strong zero trust principles for the highest security, and even allows you to embed the overlay directly into you game/app using an SDK. If you prefer to share publically, you can use zrok.io, zrok.ia Ngrok replacement for public sharing (incl. TCP/UDP tunnels) which is built on top of Ziti.
You could use zrok.io, protected by the ‘front door’ feature being released today. Then you do not need users to have VPN tunnels, no need to port forward, easily accessible by anyone who is authenticated.