Post guidance
1080 x 1440 px (3:4) is the format that survives both places at once: the feed shows it in full and the profile grid, which crops everything to 3:4, has nothing left to cut.
Square 1:1, portrait 4:5 and landscape 1.91:1 still publish normally in the feed. They are simply trimmed in the grid, so keep the subject centred if you use them.