Tailscalar here. Use https://tailscale.com/kb/1242/tailscale-serve/. It is a reverse proxy inside tailscaled. It will handle HTTPS certificates for you too. As an example, here’s a sample HTTP server proxied to both my tailnet via tailscale serve and to the world with Funnel.
Also as far as I know you need to use Serve in order to use Funnel.