Okay to be clear this won't always work and definitely won't always work well. But it's something. It's not the dark mode we deserve. But it's the one we need right now.
- Create a new bookmark in whatever browser.
- Set the target or location of the bookmark to the following snippet.
javascript:(function(){document.documentElement.style.mixBlendMode = 'difference';document.documentElement.style.filter = 'hue-rotate(180deg)';})();
- Profit.