ASP.NET Zero solution for both identityserver and client - identityserver4

Question

Before getting into the issue, let me tell you what I am trying to achieve.
I need to implement sort of SSO in all of my applications. For which I want to use ASP.NET Zero solutions as
SSO Provider as well as Clients.
Is it possible or am I overthinking?
I am using ASP.NET Zero template: ASP.NET Core - MVC & jQuery
I am very new to IdentityServer and OpenId so please excuse for my silly mistakes if I have made.
In one of ABP project, I have added a static client to IdentityServer AppSettings like below.
First project's AppSettings - Hosted application
{
"ClientId": "localhost",
"ClientName": "MVC Client Demo",
"AllowedGrantTypes": [
"implicit"
],
"RequireConsent": "true",
"ClientSecrets": [
{
"Value": "test"
}
],
"RedirectUris": [
"https://localhost:44302/signin-oidc"
],
"PostLogoutRedirectUris": [
"https://localhost:44302/Account/Login"
],
"AllowedScopes": [
"openid",
"profile",
"email",
"phone",
"default-api"
],
"AllowOfflineAccess": "true"
}
Now from my second ABP project (localhost), I am trying to enable OpenId to authenticated through above server.
Second project's AppSettings - Running on localhost
"OpenId": {
"IsEnabled": "true",
"Authority": "https://[applicationname].azurewebsites.net/",
"ClientId": "localhost",
"ClientSecret": "test",
"ValidateIssuer": "true",
"ClaimsMapping": [
{
"claim": "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier",
"key": "http://schemas.microsoft.com/identity/claims/objectidentifier"
}
]
}
However I am not getting any error, in logs I can see there is a message that says:
AuthenticationScheme: Identity.External signed in.
And a cookie is being created with key "Identity.External" but login-is not happening successfully.
Inside AccountController below line returns null and that resulting into unsuccessful login.
**var externalLoginInfo = await _signInManager.GetExternalLoginInfoAsync();**
if (externalLoginInfo == null)
{
Logger.Warn("Could not get information from external login.");
return RedirectToAction(nameof(Login));
}

Answer 1

Try adding
JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();
JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Add("sub", ClaimTypes.NameIdentifier);
before services.AddAuthentication()
This will map sub claim to NameIdentifier claim so GetExternalLoginInfoAsync will not return null.