Luukkonen played for Finland in the U18 and U20 World Junior Championships. He won a gold medal at the U18 World Juniors in 2016, stepping in as starter when Leevi Laakso got sick and the silver medal in 2017. He won the gold again at the 2019 World Junior Ice Hockey Championships in a 3–2 victory over Team USA and was named the media's pick for best goaltender of the tournament.