Add an account
One sign-in covers both. Instagram Business accounts do not have a login of their own here, so Meta reaches yours through the Facebook Page it is attached to. If no Instagram is attached to your Page, only the Page connects.
Why X is missing
Since February 2026, new developers on the X API pay per use: $0.015 to create a post, and $0.20 if that post carries a link. The flat tiers closed to new signups. Every other platform on this list is free to post to once the app is approved, so X is the only one that would force a meter onto the product, and metering is the complaint people leave over.