I don't know if you use Firefox, but I do.
I find it to be the best browser, it has the best privacy features and best add-ons and also themes.
(I know it used to crash a lot for some people, but somehow it has been working perfectly for me.😁)
I found out it's not too difficult to make a theme yourself so I had to make one myself.
And I made the darkest and blackest theme ever, I did not found this dark theme from the store yet.
So if you also like dark themes, then you can try it if you use Firefox:
This is how it looks like, new tab pages are also black.