Scaling problem with Qt apps

Hi I have problem with scaling for Qt apps. when i open Kolourpaint scaling is too small i have Ubuntu 18.04 and install from snap and apt i first report to bugs.kde.org and they tell me to report here https://bugs.kde.org/show_bug.cgi?id=407668

Kolourpaint its not only app with problem , anydesk , filezilla , pylon viewer , dukto , stacer , vmware horizon