Interestingly, Samsung's mobile browser actually has a "sensitive" mode that will either be light or dark depending on time of day in your locale, or you can set it to perma-dark as I do. Google Chrome on mobile, however, has very spotty record with dark mode even when it's explicitly enabled, oftentimes not working at all. This is on my Pixel 7 Pro so YMMV.

Brave has a dark mode but it looks like it is an afterthought, designed by the mentally deficient. The approach seems to be to invert most colors so it ends up looking hideous. Very inferior UX. But because that has native adblocking and I also use the Leo AI I end up using it a lot anyway.

All mobile devices should at least have custom UI packages that enable "always on dark modes" along with further features such as automatically terminating blue light after sundown. There may be some apps that offer these functions now - I haven't checked.