If you are not using SSL: http://<your_home_assistant_url_or_local_ip>:<port>/auth/external/callback
This should be the direct url to put in the developers app. Too bad of course it is not correct. The site is telling:
If you receive an INVALID_CLIENT: Invalid redirect URI error while trying to authenticate with your Spotify account, make sure to check the Redirect URI in the address bar after adding the new integration. Compare this value with the Redirect URL defined in the Spotify Developer Portal.
Also tried, but i just restarted and did it again, now its working, Unfortunately, not many more functions as the variant of the card from HACS. You will not see lists, you can only play something that is already running. I was actually looking for something in which I can fully control Spotify. Was for my old parents of almost 90 years old That they can choose a playlist and play via a screen. This does not have this option.
FIXED!!! For everyone getting bad URI redirects, etc, this is what I just did after reading all of the articles on this.
First off - the main issue I found was that in my config.yaml, under homeassistant, I had the internal URL with an extension of /lovelace/standard/blah blah, instead of JUST http://myHAip:port/ That’s it!