Download photo grid from the App Store. Best app to use to make panorama pictures fit in Instagram.
Select single HD.
Select which photo album your panorama picture is in.
Select the reframe button (middle button). Then select the horizontal widening button with the arrows pointing out ⬅️ ➡️ like so. Panorama picture should look like this
Select the three dotted button on the top right before the green button to open the picture in Instagram
Add a filter is you choose. I suggest editing the picture before loading it to photo grid
I delete the caption that is automatically inserted by photo grid and add my own. Now you can upload any panorama picture to Instagram!