On a cold Chicago morning last month, Gary Marx, a veteran investigative reporter, took his dog for a walk and then strolled over to the affluent Lincoln Park neighborhood. After being buzzed into the courtyard of a large house, he hand-delivered a letter urging the intended recipient to buy — or at least invest in — Mr. Marx’s journalistic home of more than three decades, The Chicago Tribune.

“It’s one thing to put your name on a museum,” Mr. Marx said, summarizing the contents of the letter in an interview, “but this is to save an institution that really safeguards this city.”

Along with a Tribune colleague, the investigative reporter David Jackson, Mr. Marx undertook his unorthodox campaign after it was disclosed in November that Alden Global Capital, a New York hedge fund, had acquired a large stake in Tribune Publishing, the parent company of Chicago’s biggest daily.

Journalists are wary of Alden because of its cut-to-the-bone management strategy. In 2018, a group of writers and editors at the Alden-owned Denver Post published a special package devoted to attacking the company, which had enacted deep staff cuts at the paper. The lead article blasted Alden executives as “vulture capitalists.”