This addon is garbage. Use Stylus instead. Unfortunately you will still have to deal with userstyles.org (the ones behind this extension) and that piss poor website.

See why it's called spyware: https://en.wikipedia.org/wiki/Stylish#Privacy_issues

Why is Mozilla the self proclaimed Privacy Advicate and Savior of the Web even allow spyware on its extension store? But when I review APB and its shady practices and history Mozilla allows the developers to censor AS IN REMOVE the review.

This addon isn't what it used to be. Now the only thing it does is not working! I installed 2 dark themes for Yandex and not only none of them appeared as "installed" in the addon (next to "library") but they also didn't have any effect on the yandex page.
Deleting from the browser, it's not worthy to waste my time with this crap.

Spyware; use Stylus instead.

Spyware

spyware people, spyware people!!!

Not only does this use an excessive amount of CPU (terrible battery drain on Android), it really should be removed from Firefox add-ons because it's spyware.

Made firefox 68 completely unuseable for me. If you still use it, back up your styles and try stylus instead, much faster.

Bad addon
Because of privacy

Very performance heavy, uninstalled because of it. Was taking like 60% of my CPU, and from what i've heard, is really invasive about privacy. So fuck it.

I mean, if you chose mozilla for privacy, don't choose this.

Using way too much CPU, disabling it dropped firefox idle CPU usage from 20-30% to 1-3%. (Tested on Ubuntu and Arch Linux, on an Intel i7 6th gen laptop CPU)

Can't download anything.