only shows up when in 'dark mode'.

that is some amazingly crap UX. who the hell thought this was a good idea?

Ambient mode is a dark mode specific feature. If you don’t use dark mode then it’s not going to do anything.

Completely hiding it in normal mode isn’t the best choice, but it is somewhat understandable.

In dark mode. Don't see it. Windows 11, Edge and Firefox.

Windows 10 and Firefox. In dark theme. No Ambient mode.

this makes sense. I stopped doing per site dark mode and just use the darkreader extension to make everything dark mode, so the option never appears.