We have opened up the ability to use the Dynamic Content block for Instagram DM Automation. If you are trying to send dynamic content via API to your contacts, now you are able to just as you are in Messenger. We recommend only developers that are comfortable with APIs and JSONs to use this feature.
To use this feature, go to your Flow Builder, edit a Flow, and add a Dynamic Content block there. Currently there's no way to test this feature for IG.
Learn more how to use this feature here