There was a regular service from Londonderry to Glasgow. Usually two or three sailings a week. The main cargo was often freight or livestock and passengers were top up income, so the fares were very cheap. Folk went back and forth all the time. (A lot of Donegal folk still go to Scotland for work, to this day. Some things don’t change.).
By way of example, Belfast Chronicle of 20th September 1828 reports arrivals from Glasgow at Londonderry 9th to 15th Sept 1828 which included the Wyse a steamer with merchandize, the Glencairn with coals and the Britannia, a steamer with merchandize.