Published to IIS such that the site is not deployed at the root level and after login the user is redirected to the root url instead of the site url

[anujc]

I published the sample to IIS such that the site is not deployed at the root level. e.g. https://server/sites/sample and user is redirected to the root url (https://server) instead of the site url (https://server/sites/sample)

I could be wrong but it looks like the issue occurs because of Redirect url is specified as the root url "/"
public void SignIn()
{
// Send an OpenID Connect sign-in request.
if (!Request.IsAuthenticated)
{
HttpContext.GetOwinContext().Authentication.Challenge(new AuthenticationProperties { RedirectUri = "/" }, OpenIdConnectAuthenticationDefaults.AuthenticationType);
}
}

[jmprieur]

Indeed, you would need to change the Redirect URI, both in the code, and in the App registration for the application