You can secure your tunnels using the Access menu and then adding an application. It should be somewhat straight-forward but you're basically looking to create an access policy and then adding the rules you want. For example a simple one is to add an allow rule for certain emails. When you enter your email an access code will be sent to you before you can access the application resource. That's just one of many ways to secure it using their application config and access policies.
I used to expose my Vaultwarden instance with it, but I think it didn't work with the protected CF login.
Likely because the apps need access to the host and the policies were likely blocking it since it's non-interactive.