var forwardingOptions = new ForwardedHeadersOptions()
{
ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
};
forwardingOptions.KnownNetworks.Clear(); //its loopback by default
forwardingOptions.KnownProxies.Clear();
app.UseForwardedHeaders(forwardingOptions);
этот блок кода из другого ответа решил проблему для меня. .net Core X Forwarded Proto не работает