This change is unrelated.
Also I said in a review about how we shouldn't be doing this.

I don't understand what this is doing? It looks wrong?

This area needs some tidying.

Also we need this line if the palette isn't explicitly set to something else.

it is as since StylePrivate is mostly binding QPalette colors, all its uses should be eventually removed

it's getting (and eventually creating if didn't exist yet) the attached property Kirigami.Theme, which is a subclass of the public symbol PlatformTheme, which is guaranteed to exist at that point

definitely a mess, yeah :)
Anyways, the idea is not to use anymore the qapplication's palette as areas of the application window can use a completely different palette.
so m_theme->palette() will fallback to QApplication::palette() when the runtime integration to kcolorscheme is not installed, and instead will be built upon KColorscheme when D7940 is installed

I meant specifically the setInherit

that's also exposed in QML and you have that being explicitly set there.

ouch yeah, that's actually a leftover :)

and disconnect from the old window

This is bad

If some other place miles away in a random lib in a different place in the UI, sets a colour, it will be wrong.

Why meddle with the global loader if you're passing it as an arg anyway?