Does exactly what I hoped and wanted it to do. Facebook and Instagram at night are now tolerable because the background is black and the words are white. Love it! Can't recommend it enough! Thank you Joue!

Edit: It is messing up Twitter though. Maybe because Twitter seems to have its own dark mode?

Edit2: Yeah, turned off dark mode on Twitter and it partly solved the problem. Text is now rendered ok but images still have a weird look (like negatives from film)