Hello i have exactly the same problem on Manjaro up to date.
I have found this but don't help me :
https://forum.qt.io/topic/126822/cura-does-not-start-qqmlapplicationengine-failed-to-load-component
And it seems that Ultimaker have deal with this.. but nothing work since Cura any of the 5xxx or 5 beta version..
And others and many other post but any help me..
https://stackoverflow.com/questions/18024207/qt-warning-qqmlcomponent-component-is-not-ready
https://forum.qt.io/topic/54517/solved-qqmlcomponent-component-is-not-ready
I have see same problem here.. so tell on the post: