You can set the message type to "system":

message = {
    "text": f"Today's reading: {passage_reference}",
    "isGroupPlanPassage": True,
    "passageReference": passage_reference,
    "passageData": {
        "planId": plan_data.get("groupPlanID"),
        "passageNumber": current_passage_number
    },
    "user": {
        "id": system_user_id,
        "name": app_name,
        "image": image_url},
    "type": "system"
}

You should be able to make it look different based on this and all the user info you pass through should be attached to the message.

https://getstream.io/chat/docs/python/silent_messages/

If you're using the react sdk on the front-end you should read this to customize it: https://getstream.io/chat/docs/sdk/react/guides/customization/system_message/