Well, I've been working on the workaround suggested by various posts with limited success, but I think this may be the ticket until they get the gremlins figured out.
Setup where I had the problem: Firefox (also Chromium) on Linux Lite
I login using Facebook.
Workarounds: Firefox User-Agent Switcher [OR] Chrome User-Agent Switcher set to Microsoft Edge
See attached screenshot.
The last row in the panel UI is dedicated for the control options including a button (at the lower left) to change the UA to its default value.
Update: I found this info. You can specify a particular URL or domain so that UA is only applied to that URL or domain (read FAQ for detailed description).
For this Spotify issue: in the box at the bottom where it says all_urls, replace that with spotify.com. The extension/addon remembers it for future broswer sessions.
Solved! Go to Solution.