For Qt 5.15.2, an official standalone "offline installer" (like the .exe files for 5.14 and earlier) is not publicly available for open-source users. Official offline packages for this specific version are restricted to commercial users via the Qt Account portal.

Open-source users can still install Qt 5.15.2 using the Online Installer or by building it from source. 1. Recommended: Use the Online Installer

This is the standard way to get 5.15.2. You must log in with a Qt Account to use it. Download: Get the Online Installer from the official site. Locate 5.15.2: Launch the installer and log in. Select Custom installation.

In the component selection, click the Archive checkbox and hit Filter. Qt 5.15.2 will appear in the list under the "Qt" tree. 2. Alternative: Download Source Code (Offline)

If you need files for an air-gapped machine, you can download the full source code as a single archive and compile it manually. Install Qt creator 5.15.2 - Qt Forum

Issue 4: macOS "Damaged" Error

Fix: Run:

sudo spctl --master-disable
xattr -d com.apple.quarantine qt-opensource-mac-x64-5.15.2.dmg

6. Critical Technical Notes

• Qt Account Requirement: Even when using an offline installer, the initial setup often requires linking the installation to a Qt Account to associate the license.
• Compiler Dependencies: The offline installer includes the Qt libraries but does not typically include the C++ compiler. You must ensure the appropriate compiler (Visual Studio, MinGW, GCC, Clang) is installed on the target system prior to installing Qt.
• Maintenance Tool: The installation will include the MaintenanceTool, which allows for adding or removing components later. However, adding new versions will require an internet connection via the Maintenance Tool.

Step 2: Understand the Directory Structure

On the 5.15.2 page, you will see multiple subdirectories. Here is what matters:

• single/ – Contains individual component packages (not recommended for beginners).
• submodules/ – Source code broken into parts.
• Root files – Look for files named qt-opensource-windows-x86-5.15.2.exe, qt-opensource-linux-x64-5.15.2.run, or qt-opensource-mac-x64-5.15.2.dmg.