The 20-year-old joined the Magpies from A-League side Central Coast Mariners in January 2023 before spending the remainder of the 2022/23 season on loan at Scottish Premiership outfit Heart of Midlothian.
He then carried out a season-long loan with Eredivisie side FC Volendam the following term.
Kuol completed a positive campaign with Newcastle's under-21s side during the second half of the 2024/25 season, scoring eight times in all competitions as well as being shortlisted for April's Premier League 2 Player of the Month award.
He will now be reunited with former Under-21s lead coach Diarmuid O’Carroll, who joined Sparta Prague as a first team coach earlier this summer.
Everybody at Newcastle United would like to thank Garang for his contribution to the club and wishes him well for the future.