I checked it, cause I always use two monitors. I was wondering what you were saying about the fact that after blocking a session, it only showed the login form on one screen. The truth is that it is not visible on the secondary monitor, but if you move over it or click with the mouse on the secondary monitor, you will see that the login screen is visible. That is, it is always available on all connected monitors. It is not clear to me whether it works like this …
That’s not currently possible. KWin for Plasma 6.1 is introducing a brightness modifier for HDR displays, the plan is to later on use this for regular SDR displays as well. At that point we can look into how best to combine hardware brightness with color-transformed brightness.