FULL STEPS:

1. Open any site using Moodle (e.g. this one) 

WHAT YOU EXPECTED:
The website’s dark theme is automatically turned on (prefers-color-scheme), since my browser is also in the dark theme. Or at least there will be a dark theme switch.

WHAT ACTUALLY HAPPENS:
The light theme of the site is always used, although I have a browser in a dark theme. And there is no dark theme switch.