[4] He made his senior debut in the last game of the 2017 1. deild season as an already relegated Grótta lost 2–1 to Leiknir Reykjavík.

In the 2019 season, Hákon played in all 22 matches as Grótta became champions and were promoted to the top tier Úrvalsdeild for the first time.

[7][8] Hákon made his Allsvenskan debut for Elfsborg in a 1–0 win against IFK Göteborg on 1 October 2021 and proceeded to play in the next four matches.

[10] On 26 January 2024, Hákon signed a contract until June 2028 with Premier League club Brentford, for a reported £2.6 million transfer fee.

[11][12] He made his Premier League debut against Brighton & Hove Albion as a first-half substitute on 28 December 2024.