Adding OpenCV libraries to a QT5 project in Ubuntu 20.04

I’ve recently gained interest in OpenCV. The problem with this is, that in most modern tutorials and walkthroughs it seems like the go-to language for working with this C-library is Python. I have an unreasonable antipathy towards this snake of a language and although I intend to fight through it some day in the future, at the moment I have more important stuff to deal with, so I intend to experiment with OpenCV in my own way - with a blend of noobie C++ and QT. In this quick note I’ll document for my (and whomever happens to land on this blog…) benefit the process of building a recent version of OpenCV on Ubuntu 20.04 and what arcane line to insert into the dark lord of K-prefixed apps - QtCreator. ...