SelectionRectangle is fiddly to get working by default

https://doc.qt.io/qt-6/qml-qtquick-controls-selectionrectangle.html#selectionMode-prop says

Drag will only be used if it doesn't conflict with flicking. This means that TableView will need to be configured with interactive set to false, or placed inside a ScrollView

But setting interactive: false is rather drastic, and there's another option since https://codereview.qt-project.org/c/qt/qtdeclarative/+/569486 : set acceptedButtons: Qt.NoButton. So if there is code that is assuming that it should only work if the inherited Flickable is non-interactive, that needs to change in 6.9.

Ideally selection by mouse should be possible with minimal code. Even the snippet doesn't work, the way it's written. (src/quickcontrols/doc/snippets/qtquickcontrols-selectionrectangle.qml)

Maybe we still have some conflict between flicking and selection on touchscreens though; needs investigation.

There's also the conflict between selecting text if your delegate is a TextField, vs. selecting cells. I suspect that should somehow be resolvable too, but it requires more thought.