Solved KDE file dialog for non-KDE applications

Continuing from this post, are there KDE-Plasma users here who have managed to get non-KDE applications to use native KDE file dialog?

I can not do without Firefox and Libreoffice and both these applications currently use a different file dialog of its own. I have tried deskutils/plasma5-xdg-desktop-portal-kde in the past to make Firefox use KDE file dialog, without success.