Chromium Version: 71.0.3578.80 (Official Build)
OS: Ubuntu 18.04 (64-bit)

This appears to be an issue with Chromium only, not with Chrome. I can play songs from open.spotify.com in Chrome, but not in Chromium, even though chrome://settings/content/protectedContent has always been on.

What steps will reproduce the problem?
(1) Log into open.spotify.com
(2) Notice the "Enable player in your browser" screen
(3) Click "Go to support site" and follow the instructions for Chrome, which are to make sure the "Allow site [sic] to play protected content" option above is enabled.