Spoof prefers-color-scheme (auto-theme sites that support it)

[Madis0]

Prefers-color-scheme state light/dark should optionally be toggled by the VivaldiFox theme, as set by settings "default theme" and "night theme".

[nt1m]

It's not something I can do with the current API unfortunately.

There is a pref to do that however, I think it's ui.systemUsesDarkTheme, and you can set it to 1

[4-FLOSS-Free-Libre-Open-Source-Software]

There is a pref to do that however, I think it's ui.systemUsesDarkTheme, and you can set it to 1

ui.systemUsesDarkTheme	true

[jscher2000]

FWIW, in Firefox 95+:

https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/API/browserSettings/overrideContentColorScheme