Hi,
I'm no expert. Neither with qt, nor with opencascade - so I can't tell you, what's right.
I only can tell, how things works for me.
I use debian stable and opencascade stuff works with dev-packages from debian as well as self compiled variant from git.
With qt I had lot of starting troubles, especially when I switched to cmake. I have several qt installations of different versions - installed by qt binary installer.
Opencascade has troubles with qt6 so I stayed with qt5 - which actually is 5.12.11 on my system.
I wrote the interface.cmake extension, cause I had troubles to use the qt-toolkit I want.
You should NOT ignore the qt-warnings. I guess you use dev-libs from your linux box. May be you need to install some more qt-libs? Don't know.
When I realized the ease of use of the qt-online installer, I never tried system stuff again.
... by the way: I removed all cavaliercontour stuff from kutecam. So one dependency less