Do not rely on the online installer for critical infrastructure. Use aqtinstall to download the entire Qt 5.15.2 source and binaries once. Archive that folder on your company network drive. You will thank yourself two years from now when the online installer has deprecated 5.15. Do you still use Qt 5.15 in production? Or have you moved to Qt 6? Let me know in the comments below.
This is the gold standard for professionals: qt 5.15 offline installer
But why all the fuss? And why should you care about an offline installer in an era of fast internet? Do not rely on the online installer for