That's the whole point -- I don't want to be able to directly connect to it. I want to be able to provide my own URL which proxies to the local Channels DVR Server HTTPS interface (the one provided by the Go backend).
This is for when I'm not at home and don't want to directly expose the backend to the Internet using port forwards. I'd rather use a Cloudflare Tunnel which provides another layer of abstraction (admittedly, security through obscurity) by proxying foobar.mydomain.com to the Channels backend.
Presumably the Channels server publishes its IP (and maybe port?) to a centralized Channels service which provides the correct address information for remote Channels clients. I'd just like to be able to override that and provide a static URL of my own which I'll make sure ends up getting reverse proxied to the Channels server address and port.
Similar to what's described here, which I have set up for Plex (sans the access control stuff which I decided I didn't need): Securing self-hosted Plex with Cloudflare Tunnels - Mirio Blog.