> When you use the tailscale serve command with the HTTPS protocol, Tailscale automatically provisions a TLS certificate for your unique tailnet DNS name.
So is the certificate not valid? The 'Limitations' section doesn't mention anything about TLS either:
https://tailscale.com/docs/features/tailscale-services
Then you can access stuff on your tailnet by going to http://service instead of http://ip:port
It works well! Only thing missing now is TLS