As a free agent in the off-season, McKenna extended his career in agreeing to a one-year, two-way contract with the Ottawa Senators on July 1, 2018. He joined AHL affiliate, the Belleville Senators to begin the 2018–19 season. After six games with Belleville, McKenna was recalled by Ottawa. He appeared in 10 games with the Senators, posting 1-4-1 record before he was traded along with Tom Pyatt and a 2019 sixth round draft pick to the Vancouver Canucks in exchange for Anders Nilsson and Darren Archibald on January 2, 2019. He was waived after backing up Jacob Markström for two games, with the Canucks' intention being to reassign him to their AHL affiliate, the Utica Comets. He was promptly claimed on waivers by the Philadelphia Flyers as they dealt with injuries to goaltenders Brian Elliott, Michal Neuvirth, and Anthony Stolarz. McKenna made his Flyers debut on January 8, 2019 against the Washington Capitals. He was the seventh goaltender to start for the Flyers in the 2018–19 season in only the 43rd game. On January 30, 2019, McKenna agreed to a 14-day conditioning loan with the Lehigh Valley Phantoms. He went 2-1 during the stint while playing for an AHL-record thirteenth franchise.