Östman played hockey in Sweden with
HV71's
SuperElit junior team, as well as some stints with their
Swedish Hockey League (SHL) team. Following three seasons with HV71, Östman opted to play in America, joining the
Chicago Steel of the
United States Hockey League (USHL) for the
2019–20 season. He said that the USHL is "a few levels better" than the SuperElit league. During the season, he maintained a 2.34
goals against average (GAA) and a .913
save percentage. Following one season in the USHL, Östman committed to the
University of Maine's hockey team, the
Black Bears. In his
freshman year, he achieved a 3–6–1 record, managing a 3.77 GAA and a .902 save percentage. On 3 April 2024, the
Seattle Kraken signed Östman to a two-year,
entry-level contract. On 8 April, before joining the Kraken's
American Hockey League (AHL) affiliate, the
Coachella Valley Firebirds, he was named the Outstanding Graduating International Student by the Maine Business School. During the season, on 8 April 2025, Östman made his NHL debut with the Kraken in relief against the
Utah Hockey Club. ==Personal life==