I usually try to not answer in page 5 to OP, but I think that this direction was not explored.
I’m currently tweaking the UI over at WagerX.io and I’m torn on a feature.
As somebody using dark mode pretty much everywhere possible, I'll tell you about something more to test out:
* some browsers, like Vivaldi, have some sort of dark mode override, making even actual "light" websites dark; the problem is that even images get inverted and some will look bad/unrecognizable
* an addon from Chromium was doing the same
What I want to also tell (apart of "you may want to test that too") is that there are more ways to have dark mode on, some may not even bother to set it from website.
Overall, ignoring dark mode in 2026 is not a good business direction imho.