Ingress (sidebar) doesn't work

[celynw]

When I look at the browser console for another addon where ingress does work, there's a request which looks like this:

GET http://IP_ADDRESS:8123/api/hassio_ingress/<token>/api/auth/onboard

Although the entry is red and it says "503 Service unavailable", it also has a XHRGET indicator. Also, the cookie in the request headers includes a ingress_session=<key>, and obviously the page displays normally.

Before I added "ingress_entry": "app" to the config.json, I got 404 errors when accessing Navidrome from the sidebar. The browser console has a failure is like this, with no ingress_session in the cookie:

GET http://IP_ADDRESS:8123/app/

I added "ingress_entry": "app" to the config.json, and this seems to get a bit further. Although I didn't see other people use this feature...

Now, I get an error about X-Frame-Options The loading ... is denied by “X-Frame-Options“ directive set to “deny“. This doesn't seem to be a response from NGinx from withing the addon container. Idk what to do about this. The docs aren't much help