Jack made his senior debut for Brommapojkarna at the age of 15 in a Svenska Cupen game against Norrköping in March 2017.
[5] On deadline day, 4 April 2019, however, the loan deal was converted to a permanent transfer, before Lahne had had the chance to play for Amiens.
[6][8] Lahne made his Allsvenskan debut for AIK on 8 April 2019, coming on as a substitute for Saku Ylätupa in a 0–0 draw against IFK Norrköping.
[10] On 1 July 2019, Amiens exercised their option to end Lahne's loan deal with AIK prematurely.
[17] On 29 July 2024, Lahne returned to the Norwegian First Division, joining Egersund on a permanent deal following his departure from Amiens.