This post is showing you where to get SSIS installer for Visual Studio 2019. SSIS for Visual Studio is no longer install from SSDT. SSDT is already end of the story. SSIS is an individual project by itself. You can download it from https://marketplace.visualstudio.com/items?itemName=SSIS.SqlServerIntegrationServicesProjects (link still available today). Run Microsoft.DataTools.IntegrationServices.exe once you have downloaded.
Start Visual Studio 2019 you will get almost the similar screen below. Click Create a new project.
Click on Integration Services Project, Click Next.
Enter the Project name and Location. Click Create.
You will now see the SSIS package.