Does SPO support Instagram?

Yes, we can support Instagram link preview shown in direct messages.

Since April 2017, Instagram has enabled link preview sent in direct messages. Though we cannot find the official Instagram link preview spec, we find that it should be the same as the dimension ratio of Facebook link preview. Since Facebook & Instagram share the same social meta tags, you can upload an image of 1200px X 630px (1.91:1 width-to-height) to Facebook link preview. And Instagram will display a large link preview same as Facebook.