List of steps to reproduce (step by step, including full links if applicable):

• Visit https://test.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering on any WMF project

What happens?:

• Notice the lack of the option to select "Modern"

What should have happened instead?:

• The skin "modern" should be available to select

Reported on enwiki by Nthep in https://en.wikipedia.org/w/index.php?title=Wikipedia:Village_pump_(technical)&oldid=1038335382#modern_skin_on_Commons

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc: