Anyone happen to know if this is a bug? Qt style override doesn't seem to work anymore on gwenview, regardless the option (kvantum, breeze,windows..) you choose. Since they changed the background settings from slider to fixed, I used to run gwenview in a dark kvantum theme override. Doesn't seem to work in plasma 5.24. Works fine in other qt apps I've tried and are set up this way.
Edit: Just noticed konsole has the same problem. Parts, such as toolbar, turn gray-ish. They don't adapt the kvantum styling.

Edit: Fiddled a bit with a couple of things and it's working now. https://imgur.com/a/GhQqfgU. Gwenview and some adapt the qt override.