I set option in “Power Settings” to turn off monitor on press of “power button”.
Screen turns off, then immediately gets back on.
Also, dimming screen only works in GameMode, setting brightness or “dim after x min” in DesktopMode does nothing.
I tested setting Power Profile for activity, running app in Activity, but I saw no effect after timeouts or hitting the button.
I think op may want screen off and not sleep mode. Power button turns the screen off because it puts it to sleep and therefore won’t download anything.