I often use dark themes when I use Arch Linux, but I don’t want some pages switch to night mode automatically when I browse them.
I added the value ui.systemUsesDarkTheme to 0 in about:config as it is mentioned in zhullyb’s blog1.
But I found out that with the recent update of firefox to 95.0, this doesn’t seem to work anymore2. So I found another way in the forum: change the value of layout.css.prefers-color-scheme.content-override3.
Where 0 indicates dark mode, 1 indicates light mode, 2 indicates the system theme color and the default value of 3 indicates the Firefox theme color.
Therefore, we need to change this value to 1 to force the page to use day mode.