I plan on going to Keelung on Sunday, and I just assumed I could take the bus from Taipei Main Station like I’ve done so many times. But do you know if the buses will be running as usual? Will I need a ticket in advance?
I don’t see any reason why they should not run.
Long distance buses should run just fine. Local buses will be using a holiday schedule.
They could be packed with tourists/people headed to Guanlishan to clean their relatives tombs, that would be the only problem.
You can always take the Keelung buses from other stations, like from Xindian or Ximen or Banqiao or Taipei City Hall.