How to make Chrome pages detect if which mode is enabled (light/dark mode)

These days every other webpage support, light/dark mode, and there I have seen that there's an option to select "Use System Theme", how can I make these website know which mode I am in. Currently this doesn't work though at least in Zorin OS 16 Pro.

It will not work on any distro - because it is how Chrome is encoded, not the distros.
I apply dark mode if using a Chrome based browser by using chrome://flags
Auto Dark Mode for Web Contents
enabled for selective inversion of non-image elements

How about FireFox then?

I use Chrome Extension DarkReader to do the job. and it works okay, but sometime not so okay..

That is true for them all. They are a bit hit and miss.
The display of webpages is determined by the .css of the webpage - not by your local machine.

got it.. so a hot key to DarkModeReader is my best friend here..
I wonder if we can run a script or something which presses the hot key when we switch the system from light to dark mode, which would do the transition ..