The process takes 10–20 minutes depending on your drive speed. No internet connection required after the installer starts.
sudo apt install build-essential libgl1-mesa-dev libxcb-xinerama0-dev qt 5152 offline installer
Check the tab. If 5.15.2 isn't listed, click "Add" and browse to the qmake.exe file inside your installation's bin folder. The process takes 10–20 minutes depending on your