At the command prompt, navigate to the directory where Qt is installed.
In this case, the directory is ~/Qt (the commands shown are for linux).
Start the Qt MaintenanceTool.
Click the Settings button in the lower left corner of the dialog.
In the Network tab, select (*) No proxy.
In the Repositories tab, under User defined repositories,
double-click on the Repository field and type ONE of the following three links, for Linux, MacOS or Windows respectively,
leaving the Username and Password fields blank. This is the platform on which you are developing, not your target platform.
Click OK and then click Next to continue the installation.
Select (*) Add or remove components
Expand KDAB and check [*] Qt 5.13.1 (or whichever is the latest version).
Expand Qt and check [*] Qt 5.13.1 (the same Qt version as for KDAB).
Note that KDAB Qt and Qt versions selected should be the same.
If you do not wish to install kits for all target platforms, you can expand the selected KDAB Qt version, as well as the selected Qt version.
Be sure both the Desktop option and at least one target platform, such as Android, are selected under KDAB Qt, and also under Qt as well.
If asked, check the round checkbox (radio button) to agree to the license terms and then click Next.
Installation may take a few minutes to complete.
Click Finish to exit the Qt MaintenanceTool.