Fyi, I managed to set it up, but a couple of things that weren't so obvious that I tripped up on:
1. I didn't know what to set the repo url to, and I actually set it to the
https://hostname instead of the full path, then I used
https://hostname/repo and AI figured out to change it to
https://hostname/pubkey/repo by looking at the logs. Not sure where I was supposed to get the pubkey from after running `ngit init`
2. I used the default relays, it wasn't super obvious that I was supposed to enter the server url as a relay too. Also after setting it to my server, I see it still also publishes to 3 other public relays. Not sure how useful that is considering afaik it is only on one git server.