It wasn't working at all
Breaking it down it's this one line that causes major regressions for me though I can't immediately see why.
Can you elaborate on what was broken and why you changed it?
delegateModel property doesn't exist in QQC2.ComboBox. I was never getting a popup.
Also we didn't use to specify a delegate to the ListView
The docs you were looking at are QQC1.
Q_PROPERTY(QQmlInstanceModel *delegateModel READ delegateModel NOTIFY delegateModelChanged FINAL)``` is in `QtQuick.Templates` `ComboBox`, which this thing is.