You can make a runtime check for version

static const bool shouldSetAcceptTouchEvents = QVersionNumber::fromString(qVersion()) > QVersionNumber(5, 9, 3);
if (shouldSetAcceptTouchEvents) {
    quickWidget->setAttribute(Qt::WA_AcceptTouchEvents);
}

In D12762#259664, @anthonyfieroni wrote:

You can make a runtime check for version

static const bool shouldSetAcceptTouchEvents = QVersionNumber::fromString(qVersion()) > QVersionNumber(5, 9, 3);
if (shouldSetAcceptTouchEvents) {
    quickWidget->setAttribute(Qt::WA_AcceptTouchEvents);
}

In D12762#259949, @rempt wrote:

I wonder what the officially best code to check for a Qt version is... We usually do stuff like

#if QT_VERSION >= 0x050903

or

#if QT_VERSION >= QT_VERSION_CHECK(5, 9, 3)

in our existing code...

They do different things... @anthonyfieroni's is a run-time check which will test the version of the Qt shared libraries that's loaded into the process, @rempt's are compile-time checks that checks the version of Qt that the source is compiled against. Since there is ABI compatibility, the run-time version need not to match the compiled version. It's not an issue with the Windows/Appimage/macOS builds, but can be an issue for Linux distribution packages.

I'm fine with the patch, though, and I'm not even sure we do need a version check, since setting the attribute doesn't hurt on older versions of Qt, does it?

It does hurt... touchscreen will trigger two click events - one for the actual touch events, and one for the synthesized mouse events because older version stripped the "synthesized from touch" flag when passing the event to QML through QQuickWidget.