steps to recreate:
created a new project using the following from command line:
web new web DVCore21
opened project in VS2019
on main project, Properties, Debug, switched property “Launch” from IISExpress to IIS.
The App Url below correctly says http://localhost/DVCore21
Chrome browser loads, briefly showing http://localhost/DVCore21, but then switches to http://localhost/metadata, and shows a 404. Manually navigating to http://localhost/DVCore21/metadata works.
I reported this same problem once before in an older version, a fix was needed. That original post is located here.