That did at least fix the icons for Skanlite, but other apps like KeePass still look way off (font + colors). I tried all theme-related settings I could find to no avail.
Plasma users should not install qt5ct or qt6ct. Those are for configuring the qtlook & feel in desktop environments based upon another widget toolkit than qt, and installing them in Plasma will mess up Plasma’s own configuration settings.
It certainly looks interesting, but those barely visible black icons for the “Unlock” and “Close” buttons are a giveaway that this is not the intended look.
Speaking of icons, I just noticed that the “Open Database” icons near the top left corner is different. But both screenshots are from fully-updated Manjaro installations and show the same version of the app.
I see, did not read the whole thing. But the issue is still open and has been added to the 2.8 milestone, so this likely will get fixed. They are pretty reliable, contributed to the project myself a couple of times.