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.

zrok.io using the free SaaS together with 0Auth - https://blog.openziti.io/the-zrok-oauth-public-frontend

You could also use zrok.io. It’s an open source alternative which can be self-hosted or has a free SaaS. It also includes cool features like ‘private sharing’ (which means both sides can be private with no inbound ports). I work on the parent project.

It’s not free, though, at least $20/year on pro. Why not just pick a Ngrok alternative which can provide a fixed IP - https://github.com/anderspitman/awesome-tunneling

I was going to share the same link but you beat me :D

I work on one mentioned, zrok.io which is both open source and has a free SaaS.