Flash of white when (re)loading the app in dark theme

[fm3]

Using Firefox on Windows, I tried using dark mode and found that each page refresh (ctrl+r) would lead to a split second of the whole page being white before dark content is rendered again. Other pages like github don’t seem to have this problem. Can it be circumvented?

Just guessing, maybe only the body, but not the html element, has the dark background property in css?