It was previously possible to include any location when scheduling your Instagram post through Buffer Publish. However, on November 2, 2020, Facebook deprecated the Places Search API, which means this is no longer possible.
Now, through the API, it's only possible to include the location that is associated to the Facebook page linked to your Instagram account. You can do this by ticking the checkbox in the composer. If the checkbox is ticked and you don't have a location associated to your page, no location will be included with your post.
📝 Check out this guide from Facebook if you'd like steps on adding a location to your page. It's important that this checkbox is ticked. If it's not ticked, this will result in the location being hidden on Instagram.
It's also important to note that this works a little differently than it did previously. In the past, the location on posts scheduled through Publish would be displayed beneath the Instagram account handle. Now, the name of the Facebook page will be shown beneath the Instagram account handle, and clicking on that will take the user to the location, with both "Top" and "Recent" posts tagged with that same location.