Setting up CircleCI to compile a Qt app against a specific version of Qt

We have an app which is to be compiled against a specific version of Qt (currently in our case Qt 5.9.9, but we hope for Qt6 in the future). We are new to CircleCI, what is a minimal yaml which would work to compile the app? On the computer, qmake && make is all that is necessary, so we’re hopeful that this is not a hard problem.

I found Preinstall QT5 in images - Feature Requests - CircleCI Discuss, but it looks quite old and there were reported issues with that route.

P.S.: We’d also love an easy example of how to make the artifact available to GitHub, but we can figure that out ourselves once we have a working example of building the Qt app.