Home Assistant recently changed the way Spotify's configured so I wrote up a guide. This works with most versions of HomeAssistant but I used it with 106 & up.

Steps

• Login to the **Spotify Developers Console** with your Spotify username and password.
• Click Create a Client ID in the top right corner. A popup should appear.
• Enter Home Assistant (or whatever) for the app name. Description doesn't matter. Put "Automation" in the description. A new pop up appears.
• Click the Non Commercial button on the right hand side.
• Checkmark Website and then press Next. Next popup.
• Click all 3 checkboxes and then click Submit.
• You'll see a new page with your newly created app.
• In the top right corner, click the green button that says Edit Settings. A popup appears. We need to add Redirect URI's and nothing else.
• Create two redirect URIs. One that goes to your lovelace UI and the other to the appropriate URL. **Even if you have Nabu Casa or DuckDNS set up, just use your local http:// URL.
  • http://192.168.0.1:8123/lovelace/lovelace_default_view
  • http://192.168.0.1:8123/auth/external/callback
• Click Show Client Secret. Open up Configuration.yaml and paste the keys directly or use secrets.yaml (like I have below)
• Create a spotify key in your configuration.yaml file as shown below. I use the secrets.yaml file which is why you see !secret.

spotify:
  client_id: !secret spotify_id (OR "clientidxyz")
  client_secret: !secret spotify_secret (OR "clientsecretxyz")

• Restart Home Assistant by going to Configuration and clicking Server Controls, then Restart.
• You'll see a new notification in the bottom left corner for New Devices Discovered. Click Check it out, then click Configure under Spotify. Everything should happen automatically.
• Once that pos up, you should see a pop up that says Success. Just click Finish.
• If you have any other Spotify integrations, just click Ignore.
• You're Done!

Add Spotify to your Lovelace Dashboard