Note that: Managed identity can only be used to access same tenant and particular Azure Subscription users/resources and cannot access other tenant users/resources. Refer this SO Thread by Philippe Signoretand this MsDoc

Hence, you need to make use of client secret credential flow if you do not want user interaction to fetch the results.

If user interactive flow works in your setup, then you can make use of Interactive provider flow like below:

In TenantA I created a Multitenant app and configured redirect URL as below:

And use the below code:

• Interactive flow do not need client secret.

class Program
{
    static async Task Main(string[] args)
    {
        var scopes = new[] { "Directory.Read.All" }; 
        var tenantId = "organizations"; 
        var clientId = "ClientID";

        var options = new InteractiveBrowserCredentialOptions
        {
            TenantId = tenantId,
            ClientId = clientId,
            AuthorityHost = AzureAuthorityHosts.AzurePublicCloud,
            RedirectUri = new Uri("http://localhost"), 
        };
        var interactiveCredential = new InteractiveBrowserCredential(options);
        var graphClient = new GraphServiceClient(interactiveCredential, scopes);
        await FetchUsers(graphClient);
    }

    private static async Task FetchUsers(GraphServiceClient graphClient)
    {
        try
        {
            var result = await graphClient.Users.GetAsync((requestConfiguration) =>
            {
                requestConfiguration.QueryParameters.Select = new string[] { "id", "displayName" }; 
            });
            foreach (var user in result.Value)
            {
                Console.WriteLine($"User ID: {user.Id}, Display Name: {user.DisplayName}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error fetching users: {ex.Message}");
        }
    }
}

I signed in TenantB user:

And got the users successfully:

If the above don’t suit your environment, then instead of using client secret you can also make use of certificate-based authentication for client secret credential.