Boats to Dublin would likely have come from Liverpool so making an East -West journey across England likely for migrants. One of the earlier comments mentioned journeys to Hull by boat. I think this is the most likelt jouney my ancestors have taken but I just don't know.
Glasgow - Londonderry - Philadelphia and New York were popular migration journeys.
Some may have travelled Liverpool - New York without stopping in Ireland. see https://www.liverpoolmuseums.org.uk/archivesheet13