May the Dark Force be with you

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

Desde que lo agregé al navegador lo negro se ve de color azúl oscuro, ¿que pasó?

Dark Reader addon has a serious memory leak issue. This problem is affecting users for quite a long time.

SERIOUS MEMORY LEAK. After a month of my laptop locking up and requiring a forced restart I narrowed it down to being Dark Reader with Sepia cranked up to the maximum setting. There's no doubt this is the most effective extension for forcing websites to "go dark". Unfortunately, it's unusable if it freezes your computer every few hours. UPDATE: tried it again a few months later and still the same problem.

DAMN GOOD!