Unfortunately, Stream are not able to do this sort of migration. That being said, you are able to use our various tools and API endpoints to do this. I'll link you to some relevant documentation for chat and feeds below:
exporting - You can export the data of a feed by using the .get() method. You can retrieve up to 1000 activities with it.
If you need more than that, you will have to retrieve the missing activities with our batch method getActivities() using the activities IDs or the time +foreign id.
Reach out to email@example.com if you have further questions