Unable to install SQL Server (setup.exe), VS Shell installation has failed with exit code 1638.

The problem is likely that there's a newer version of the Visual C++ Redistributable than SQL Server is trying to install, e.g., from Visual Studio 2017. So another way to address this, if you don't need the latest C++ redistributable, is to go to Add or Remove Programs and uninstall all references to Visual C++ 2017 Redistributable. After this, the SQL Server installation should proceed without errors.