You can download Stylish here. After the downloading process, Go to bitcointalk.org click the extension go to Find more styles for this site.
Here is the style that I installed.
I'm using Stylus in both Chromium (Ie. Brave) and Firefox (Ie. Waterfox) based browsers. It is a Stylish fork without the nonsense, and it uses the same themes. Stylish used to be nice before it added user tracking, and other annoyances, but the fork cures this.
It is an accessibility need, as too many web sites don't offer a dark/night mode. I have a couple of "global themes" always ready to use: Pseudo Brightness and dark style. For Firefox I also have no more black text on black input boxe for the daytime when i don't use dark style but keep my dark desktop theme.
Messing the monitor controls is not always possible/desirable (ie. after half an hour of color calibration) or sometimes the laptop/all in one is already at the min but still too bright. And some people could just need the extra contrast anyway.