If you are using the Qt Maintenance Tool or the Qt Online Installer and only see Qt 6.x (for example Qt 6.9), you can still install older versions like Qt 5.15.x. By default, the installer hides archived versions.

To enable them:

1. Open the Qt Maintenance Tool (or run the Online Installer).

2. Log in with your Qt account.

3. On the “Select Components” page, look for the filter options at the top.

4. Enable the “Archive” option.

5. Now you will see older releases, including Qt 5.x.x versions.

6. Select the version you want (e.g. Qt 5.15.2) and install it.

This way you don’t need to manually download and build from source — the installer can fetch the archived packages for you.