The code has not changed and it still works for me. Black means that there is an issue withstanding and lighting. Which browser and browser version did you use. Which lighting mode do you use in the viewport settings?

Firefox 67.0 is the browser version. Lightning settings can be anything, let's take the default.

I am a bit confused because:

• Nobody reported anything like it
• I didn't change the code in the past week
• I just tried with Firefox 67 and it worked

Do the "flat" and "matcap" modes produce the same issue?

I didn't touch these settings ever before. I was messing them up with "lamps". Changing any of them fixes it.
Looks like these settings are in HDRI whenever I load the workshop. The first and the last one produces a black background when I show the HDRI as background and turn the bricks black as well.

Changed and saved the settings, so it's fixed for me.