Substack has hired Mark Swierszcz as its new head of partnerships in Canada as the media platform busily expands internationally beyond fast-growing U.S. and UK markets. Swierszcz, a former Google Canada exec, marks Substack’s first major hire in Canada, which has become the platform’s third-largest market worldwide. He told The Hollywood Reporter his focus at Substack will be “on building and deepening relationships with Canadian writers, publishers, creators, and media organizations. That means supporting people across different categories, helping them grow sustainably on Substack.” In Canada, as elsewhere internationally, Substack has grown as content creators jump ship from legacy media companies to sign up paid subscribers for their work and increasingly use audio and video to help do so. And San Francisco-based Substack, initially a newsletter platform that has expanded into other media, including with a newly-launched TV app, already has a Canadian connection. The company was founded by Chris Best, who grew up in suburban Vancouver, and Jairaj Sethi, both of whom graduated from the University of Waterloo in southern Ontario. They then worked …