They want 10€ just after installation. Avoid.

best

while I enjoy dark reader, it makes websites look a lot better, but dark reader slows Firefox on Android to a crawl, I just cannot take it, and after reading an Reddit post where users were complaining about the sluggishness of Firefox on Android, a user mentioned dark reader being the culprit, so I disabled dark reader.
Problem solved, sorry, not sorry

.

This add-on makes websites less painful at night.

Godsend extension, saved my eyes! Lot's of features & benefits.

Makes firefox agonizingly slow to load. not worth it.

Disabling it on a site/domain just likes to not work I guess!