Changes all websites to dark mode very reliably. There are occasionally smaller issues if pictures are in the background (text becomes hard to read).
Easily to revert to original. Very low performance penalty, which is worth to have all pages in dark mode.

It's a must to save your eyes! Some sites eventually break, however the extension can be easily deactivated specifically for those.

May the Dark Force be with you

works immediately, does exactly what I want, and has the best configuration settings! :-)