Qt5 app on Debian 10 not using system KDE theme

I just installed snapd on my Debian 10.
Any Qt5 snap I install does not use my current theme, but I am wondering is not using Qt5 at all…

I tried the following:
sudo snap install kcalc
sudo snap install keepassxc

None of them is using Qt5/KDE. Any clue?
Is something related with kde-neon extension? Should I only wait? Should I install another kind-of-library to connect my system-KDE?

On following screenshots, you can see the snap package (left) and the system kcalc (right)


samuel@woodbox:~$ snap version
snap    2.43.3
snapd   2.43.3
series  16
debian  10
kernel  4.19.0-8-amd64