.Net Core 3.1 and Angular compile verbosity in Visual Studio

Note That Output Window is designed to show reports, not Command Window. In order to solve your problem, Consider the following cases.

The Output window can be extended by adding to its collection of text panes programmatically, but out of the box with a typical project most users will see the following:

• Build: Contains messages about builds and their status (e.g. compilation warnings)
• Build Order: Same as “Build”, only the output is logically ordered for readability (vs chronological order)
• Debug: Contains messages from the debugger plus any text the application output during execution.

There may be required a proper choice after update in order to show desired reports. Clearly, VS may reset defaults after update process. So, please pay attention to this section.

Another possibility is unwanted project/solution changes after re-openning with the new VS version. This can cause some changes inside .sln or .csproj possibly.

Note that we can't reproduce your problem, but the above tips may solve yours.

Update

You can open .csproj file with an editor (without VS) and set a Target build like the following, perhaps conditional, in order to show results into the output window and automate the build process :

<Target Name="AngularBuild" AfterTargets="Build">
  <Exec Command="npm run build" />
</Target>

You can change the options from here.

check Tools > Options > Project and Solutions > Build and Run and change values of "MSBuild project build output verbosity"