When I launch a simple QML page over HTTP with the qml/qmlscene tools (they both have the same issue) the http request is malformed.
It's easy to reproduce it, you can launch a simple http server and launch a file with qml/qmlscene from it.
For exemple locally with PHP :
Then try to launch main.qml (which is a simple rectangle) with qml or qmlscene :
Then I've got this error from qml :
And this error from php server :
It works fine with the same configuration and file with qt 5.15