When adding a regular Resources.resx file into an asp.net core project that uses <GenerateEmbeddedFilesManifest>true</GenerateEmbeddedFilesManifest> and a ManifestEmbeddedFileProvider, the file provider throws an InvalidOperationException with this message:
Invalid manifest format. 'ResourcePath' must contain a text value. ''

Using version 2.2.0 of asp nugets, running in .net framework 4.7.2, lanunching from VS.

Looking into the generated assembly, I found that the generated manifest looks like this:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<Manifest>
  <ManifestVersion>1.0</ManifestVersion>
  <FileSystem>
    <File Name=""><ResourcePath></ResourcePath></File>
    <File Name="Microsoft.Extensions.FileProviders.Embedded.Manifest.xml"><ResourcePath>Microsoft.Extensions.FileProviders.Embedded.Manifest.xml</ResourcePath></File>
    <Directory Name="wwwroot">
      <File Name="site.css"><ResourcePath>AspResources1.wwwroot.site.css</ResourcePath>
      </File>
    </Directory>
  </FileSystem>
</Manifest>

The first entry in the manifest seems wrong.