Bad performance on Embedded device when rotating qml scene

[HSK_Developer]

Hello,

I have developed a QT quick application for the Beaglebone Black (console image, Kernel 4.19, Debian 10.10, Qt 5.11). I have installed qt via apt and deployed my qt application.
So far so good.
My Application is a square which can be rotated by 90 degrees. I am rotating the scene in qml through the rotation property.
But when I rotate the screen, the performance decreases. Tumblers aren't smooth anymore, switching qml pages takes longer.
The Beaglebone image seemingly does not support OpenGl natively and I haven't been able to make use of the eglfs platform.
The application runs on the linuxfb platform.
I have also seen that a patch for rotating the linuxfb has been released (https://borkedlabs.com/blog/2015/06-01-qt5-linuxfb-rotation-for-lcds/), but I don't know how to apply this patch. I would need to build qt from source, but I don't know how to deploy this qt version onto the BBB.

Do you know why the rotation affects the performance so much?
Should I switch to OpenGl instead of directly using the linux framebuffer? If so, how?
How can I apply the patch?

Thanks in advance!