This is the most critical section of this guide. If you go to the standard Qt download page today, you will struggle to find the 5.15.2 offline installer. Here is why:
You can actually download the official Qt 5.15.2 offline installer from https://download.qt.io/archive/qt/5.15/5.15.2/ (look for files ending in .exe , .run , or .dmg depending on your OS). qt 5.15.2 offline installer
For new developers, the difference between the two delivery methods might seem negligible, but they serve vastly different workflows. This is the most critical section of this guide
Never trust an installation without validation. qt 5.15.2 offline installer