POST Message to Teams Channel with Application-only Permissions Not Allowed for Regular Use Cases

Is your feature request related to a problem? Please describe the problem.

Hello,
I am attempting to use the Microsoft Graph API to send messages to a Microsoft Teams channel using application-only authentication with the following code:

import com.azure.identity.ClientSecretCredential;
import com.azure.identity.ClientSecretCredentialBuilder;
import com.microsoft.graph.models.ChatMessage;
import com.microsoft.graph.models.ItemBody;
import com.microsoft.graph.serviceclient.GraphServiceClient;

public class GraphClientExample {
    public static void main(String[] args) throws Exception {

        final String clientId = "****-2189-4dab-a9b8-28dc0f57b181";
        final String tenantId = "****-4b22-4755-a153-421da388048a";
        final String clientSecret = "F1p8Q~**************";

        final String[] scopes = new String[] { "https://graph.microsoft.com/.default" };

        final ClientSecretCredential credential = new ClientSecretCredentialBuilder()
                .clientId(clientId).tenantId(tenantId).clientSecret(clientSecret).build();

        if (null == scopes || null == credential) {
            throw new Exception("Unexpected error");
        }

        final GraphServiceClient graphClient = new GraphServiceClient(credential, scopes);

        ChatMessage chatMessage = new ChatMessage();
        ItemBody body = new ItemBody();
        body.setContent("Hello World");
        chatMessage.setBody(body);
        ChatMessage result = graphClient.teams().byTeamId("459b419d-9d5e-42cd-b59d-*********").channels().byChannelId("19%********************Gu3neGtMFiU8PSRzeaR-uL5AWU1%40thread.tacv2").messages().post(chatMessage);
    }
}

However, I am encountering the following error:
Message POST is allowed in application-only context only for import purposes. Refer to https://docs.microsoft.com/microsoftteams/platform/graph-api/import-messages/import-external-messages-to-teams for more details.
From what I understand, the Microsoft Teams API restricts POST requests in the application-only context to migration or import purposes. This means I am unable to use application-only authentication to send messages to a Teams channel.

Question:

Is there a recommended way to send messages to Microsoft Teams channels using application-only authentication in scenarios other than data migration?
If delegated permissions are required, is there an alternative method to authenticate using delegated permissions in a headless application or server environment?
Any insights or workarounds would be greatly appreciated!

Thank you!

Describe the solution you'd like.

Question:

Is there a recommended way to send messages to Microsoft Teams channels using application-only authentication in scenarios other than data migration?
If delegated permissions are required, is there an alternative method to authenticate using delegated permissions in a headless application or server environment?
Any insights or workarounds would be greatly appreciated!

Additional context?

No response

Start with the GraphServiceClient Java example in the issue and the linked Microsoft Teams import-messages documentation. Verify the documented constraints for application-only channel-message POST requests and the available delegated-authentication options for headless services. Done means documenting a supported authentication path or confirming that no supported workaround exists.