Spotipo needs a "local user" aka a user that can be authenticated directly with your UniFi controller. In the current version of the Unifi controller, this is not possible to do from the new UI, however still likely from the old UI.
Follow the below steps to do that.
Switch controller to old UI
Navigate to System -> Advanced in the Unifi controller and switch the interface to Legacy.
Add a new Admin
Once in the legacy interface, go to Settings -> Admins on your site and use "Add New Admin" button
Now use the option Manually set and share the password option.
Set the Name as
spotipo_userSet a strong password
Uncheck the "Require the user to change their password"
Specify the role as Administrator
Check the permissions as below
Now you can use these credentials for configuring your Spotipo site.