Some sites are still white. When I disable the night mode it does change to dark mode and keep switching back all the time. I hope it will be fixed with the next betas.
I use Dark Mode on MacOs but it doesn’t really work on iOS. Sites like Wikipedia are still white whereas the Dark Mode flag I added on the web browser turns virtually all websites into a black or dark gray background. Barely use Brave on my iPhone unless I’m traveling & need to watch tennis but avoid popups which it doesn’t actually do nearly as well as the MacOS version.