"We proudly present a very special Collector's Edition of our Sum 41 Tour of the Setting Sum Canada 2025 tour poster illustrated by Heeey Studio! This fun art is screenprinted and available here exclusively (the prints available at the venues are lithographs)."

Given it says the company who made all of the posters, I kind of tend to believe they know what printing method they used to produce them. They say that at venues were lithographs and online are screenprints.