Is the flank supported only for line unit o also is supported for other formation like column o square?

Thanks a lot

As I read the rules, only lines can support each other.

Thank you, I think so; but is better for the game that also other formations can support

From my reading ~ I would certainly Not expect Squares to support each other. They were intentionally isolated units with a primary focus on internal cohesion.

Columns, I would also not expect to provide support, since the formation is primarily for movement.