Tool bars and writing in app are unreadable in kavantum-dark theme

I have been using kavantum-dark theme in Lubuntu-20.04.3

Most of the apps run fine. But there are few in which the tool bars and writing in the app are unreadable. But this does not happen in other theme.

Below is a screenshot from an app (Master pdf editor) which looks fine if I change the Qt style to "Windows".

But the same app when the Qt Style is changed to "Kvantum-dark" looks like this:

The palette in the left is not visible. This is happening probably due to the reason that text color and icon color of the buttons are still black in "Kavantum-dark" style. Had they been white, then they would have been easily visible in dark background. How to overcome this issue?

The issue can only be overcome by correcting the theme. You may want to raise the issue to the developer of the theme.