Just tried these Steps today:
To run the samples:
Clone this repo
At the repo's root directory (the one containing src, samples, etc.), run dotnet restore
*** the AutoMapper fails to install ***
Change directory to the sample you want to run (e.g., cd samples/angular/MusicStore)
etc...

the log entry:
log : Retrying 'FindPackagesByIdAsyncCore' for source 'https://go.microsoft.com/fwlink/?LinkID=230477/FindPackagesById()?id='AutoMapper''.
log : The content at 'https://go.microsoft.com/fwlink/?LinkID=230477/FindPackagesById()?id='AutoMapper'' is not valid XML.
log : For security reasons DTD is prohibited in this XML document. To enable DTD processing set the DtdProcessing property on XmlReaderSettings to Parse and pass the settings into XmlReader.Create method.

Cheers