TORONTO—Hedge-fund manager GoldenTree Asset Management LP is in preliminary talks to sell its stake in Postmedia Network Canada Corp., Canada’s biggest newspaper publisher, according to people familiar with the matter.

​New York-based GoldenTree advised Postmedia’s board of its intentions last month, according to one person. The hedge fund hired Canadian investment bank Canaccord Genuity Group Inc. to help ​solicit buyers, according to those people, who added that a number of large institutional and ​Canadian ​media companies...