QT apps using wrong system themes

Flatpak apps based on QT wrong using system theme and mouse cursor, but apps based on GTK work is perfectly. I switched on “Qt5 Configuration tool” gtk2 theme, but QT apps installed on PPA correct using this configuration. That is flatpak permissions not using “QT_QPA_PLATFORM=gtk2” parameter.
These problems have been seen in VLC, Qbittorent, Audacious, Krita
What to do?
System – Linux Mint Cinnamon 20.1

Correct using theme on app instaled from repo


Broken theme style on app installed from Flatpak

This is not a valid QPA platform. Available ones are “xcb” or “wayland”. This is probably not the solution you are looking for.

(Otherwise I have no idea)