update to qt-5.14 and monitors became dark

[dmpogo]

I don't know the cause and effect, but I did update to qt-5.14 and associate recompile of the kde components, and on two desktops running nvidia-drivers, monitors became notably darker (I am rather senstive to level of light, and I came to the office few days ago after overnight update, and could not read well off monitor, thought it is a fluke, by last night I updated my home desktop, and voila, in the morning it is quite darker as well - at night you do notice it that much). In both case I had to up hardware brightness from 50% on which it sat for years to
75-90%.

In daemon.log I see

Successfully activated service 'org.kde.powerdevil.backlighthelper'

so powerdevil may be involved, but I don't find any controls of brightness in kde power settings

Anybody knows something about this ?