This looks similar to what https://forum.qt.io/topic/141297/exception-about-qt-creator-ui-on-ubuntu experienced.

Also on VMware.

I assume it has something to do with the graphics drivers. At https://www.qt.io/blog/qt-6.4-released we can see the topic:

QQuickWidget with full RHI support

With QQuickWidget you can build application user interfaces where Qt Quick and Qt Widget elements coexist. Until now this required using OpenGL. For Qt 6.4 we redesigned the class from the ground up, and now QQuickWidget is functional with all supported graphics APIs: Metal, Vulkan, Direct3D 11, in addition to OpenGL.

Can you post the Graphics configuration of your VMware player? Aso a bug report at https://bugreports.qt.io/ wouldn't hurt either.

Wops fixed https://doc.qt.io/qt-6/linux.html

sudo yum install mesa-libGL-devel

@KeithS
You're right, it does seem like a rendering issue regarding glx.

I was ssh'ing with X11 fowarding to the CentOS 7 machine, so my host machine (running Fedora 21) was actually doing the rendering. Trying to run glxgears hanged as well.

I actually tried ssh'ing from a windows desktop (with xming and putty) to this CentOS 7 machine and running glxgears, and it works! So it seems like it is a rendering issue or Xserver issue with my Fedora 21 desktop, not a Qt5 issue...

Thank you for all the help!

@Karen-Morrissey
I think because when you did ./configure to look for needed libraries, it first found those in /usr/lib64.

Why not to force the configure to use those for 32bit by adding

-L /path/to/lib/32bit -lpthread -lm -lc

to your configure command