Some older discussions about this: https://www.beamng.com/threads/forums-dark-mode.52547/ https://www.beamng.com/threads/optional-dark-theme.15389/
You could also use some dark-mode browser extensions, such as: https://darkreader.org (as always when using extensions, keep in mind they may read and modify the contents of pages you visit, with all what it can entail)
Xenforo Default theme(current theme for forum) has support for dark mode,and works fine for 3rd party plugins
On Android (not sure which version or even if this is a Samsung only thing) you fan press the power key and volume up to invert colors, I use it often and it works brilliantly. Screenshots are in normal colors so no comparisions.