This can happen if you installed build tools separately from VS. If you open Visual Studio installer and see something like Visual Studio Community 2019 (2), note the parens and number after the name, there’s your issue.
I didn’t do much troubleshooting other than uninstalling build tools and VS and reinstalling VS only. There might be a way to do it without uninstalling, I didn’t have the patience to find it.
Also, as @mentions, make sure you click on Game Development with C++ and check Unreal Engine Launcher.