ilverify fails with various file not found errors

After dotnet tool update --global dotnet-ilverify --version 5.0.0, any invocation of ilverify that includes a dll (I tried several) fails with:

Error: Internal.IL.VerifierException: Assembly or module not found: mscorlib
   at ILVerify.Verifier.SetSystemModuleName(AssemblyName name)
   at ILVerify.Program.Run()
   at ILVerify.Program.Run(Options options)

The latest prerelease also fails, but with a different message:

dotnet tool install --global dotnet-ilverify --version 6.0.0-preview.4.21253.7

Error:
  An assembly specified in the application dependencies manifest (ILVerify.deps.json) was not found:
    package: 'System.Collections.Immutable', version: '5.0.0'
    path: 'lib/netstandard2.0/System.Collections.Immutable.dll'