IdentityServer4 - missing claims from Google

TLDR; In the context of using IdentityServer4

1. How do you get email address and hd claims from Google?
2. How do you get User.Identity.Name to be populated?

I have worked through the IdentityServer quickstarts and have a working MVC client talking to a IdentityServer instance (apologies if using the wrong terminology). I am using External Authentication (Google) and do not have anything mildly complicated such as local logins / database etc. I am not using ASP.NET Identity. This is all working just fine.

I can successfully authenticate in my MVC app and the following code produces the claims in the screenshot below:

@foreach (var claim in User.Claims)
{
    <dt>@claim.Type</dt>
    <dd>@claim.Value</dd>
}
<dt>Identity.Name</dt>
<dd>&nbsp;@User.Identity.Name</dd>

<dt>IsAuthenticated</dt>
<dd>@User.Identity.IsAuthenticated</dd>

Questions:

1. I cannot retrieve extra claims (right term?) from Google. Specifically 'hd' or even 'email' - note that they don't show up in the claims in the above screenshot. How do I get the email address and hd claims from Google? What am I missing or doing wrong?
2. Note that the output of User.Identity.Name is empty. Why is this and how do I get this populated? This seems to be the only property of User.Identity that isn't set.

My setup is as follows - you can see the output of this as above:

Client (MVC)

In Startup.cs, ConfigureServices

JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();

services.AddAuthentication(options =>
{
    options.DefaultScheme = "Cookies";
    options.DefaultChallengeScheme = "oidc";
})
.AddCookie("Cookies")
.AddOpenIdConnect("oidc", options =>
{
    options.SignInScheme = "Cookies";
    options.Authority = Configuration["App:Urls:IdentityServer"];
    options.RequireHttpsMetadata = false;
    options.Resource = "openid profile email";
    options.Scope.Add("openid");
    options.Scope.Add("profile");
    options.Scope.Add("email");
    options.Scope.Add("domain");
    options.ClientId = "ctda-web";
    options.SaveTokens = true;
    options.GetClaimsFromUserInfoEndpoint = true;
});

Identity Server

Client definition

// OpenID Connect implicit flow client (MVC)
new Client
{
    ClientId = "ctda-web",
    ClientName = "Company To Do Web App",
    AllowedGrantTypes = GrantTypes.Implicit,
    EnableLocalLogin = false,

    // where to redirect to after login
    RedirectUris = { "http://localhost:53996/signin-oidc" },

    // where to redirect to after logout
    PostLogoutRedirectUris = { "http://localhost:53996/signout-callback-oidc" },

    AllowedScopes = new List<string>
    {
        IdentityServerConstants.StandardScopes.OpenId,
        IdentityServerConstants.StandardScopes.Profile,
        IdentityServerConstants.StandardScopes.Email,
        "domain"
    }
}

IdentityResource definition

return new List<IdentityResource>
{
    new IdentityResources.OpenId(),
    new IdentityResources.Profile(),
    new IdentityResources.Email(),
    new IdentityResource
    {
        Name = "domain",
        DisplayName = "Google Organisation",
        Description = "The hosted G Suite domain of the user, if part of one",
        UserClaims = new List<string> { "hd"}
    } 
};