Any way to store an incoming JSON in the liql database?

I'm not sure how you intend to use this, but here's one idea.

Support will add custom fields to different collections for you. So, you could ask them to add a custom field to the "messages" collection and store your JSON there more cleanly than in a message body. 

You could use this Create message (khoros.com) to post a message to the board you want with the JSON stored in a separate field on the message.

Your body would look like this

{
    "data": {
        "type": "message",
        "board": {
            "id": "myhiddenboard"
        },
        "subject": "JSON Post 6/5/2024",
        "body": "Todays JSON post!",
        "c_my_custom_json_field": "json_goes_here"
    }
}