Firefox automatically updated its browser last night. This, and all the other, dark mode extensions I have attempted to use no longer work. The screenshots are totally misleading.

I usually like to use this extension on Edge browser. However, it slows down Firefox, significantly. So, I disabled and stopped using it until developers fix it.

Still has its issues with certain sites, but works quite well overall.

very good

Usually good, but for some reason sometimes it becomes so heavy it crashes my whole laptop.

Workes very good, can recommend it to anyone.
However, I'm not using it anymore at the moment, because I somehow wasn't able to use any browser theme with it. Maybe I'm just too incompetent to find the right setting, but I if you want to use your usual Firefox theme I'd tell you not to use this.
But, as I said, I'm very impressed by the quality of the CSS filtering, and if you just care about that you should definitely give it a go.