Asking for money for a simple dark add-on is simply unacceptable. There are many other choices for free.

I would avoid this addon. While it works very well, as advertised, the developer charges money for it after a 3 month trial. That would have been ok with me, except it's a subscription-based model. Very ridiculous. I would have been ok with paying maybe $5 (which is fair for what it is) for an outright lifetime license. But anyways, I recommend for something similar, try using the addon called 'Dark Night Mode'. It's similar and works well out the box, has a higher rating, and is fully free. For something with more features and customization, I really like 'Dark Reader'.

Messed with pictures and layouts, also with some extensions, for example greasemonkey, couldn't use it at all and setting of night eye were also not functional. No-go for me