Comment 1 for bug 2002177

that's mostly obsolete nowadays
=> as long as the user can use system default and force dark whenever he wants = nothing is obsolete
But I agree, I have implemented this into my website (not online yet), and as I also switch night/day between light/dark theme, having app following this is a plus, not really better, but I probably miss that 4 mouse click is too much effort for some people at present.

a few comments for me later on:
- freedesktop is a Linux specification
- seems only available for Gnome and Granite
- for example no /appearence set in /org/freedesktop/ in Cinnamon or Mate
- even with GTK4, it requires libadwaita
- on GTK3 for now we can only rely on gtk-application-prefer-dark-theme
- gtk-application-prefer-dark-theme is not initialized on Windows 10, not 11

so it may be possible to implement a more accessible menu entry with force-light/force-dark, but default seems complex to get, on Linux at first, but probably more on Windows, didn't look at Mac.

It would be so much easier if GTK3/4 directly expose a reliable cross platform prefer-dark/light/default as well.
You seem to have connection with the developers: if you can suggest, please do :)