Anthony, 38, is an unrestricted free agent after finishing his first season with the Lakers. He appeared in 69 games, averaging 13.2 points and 4.2 rebounds, coming off the bench in all but three.
Meanwhile, the Celtics lost Gallinari for an indefinite amount of time after he suffered an MCL injury during EuroBasket play. There is a sense Gallinari will be out at least for training camp and the preseason.
So perhaps Anthony could serve as a stop-gap until Gallinari returns.
As for the Knicks, right now, all of the focus seems to be on a trade for Jazz star Donovan Mitchell. But there have indeed been reports of an Anthony reunion, and perhaps once the roster is closer to set, he will get another run in New York. He originally played there from 2010-17.
It does not appear Anthony will be returning to the Lakers, who decided to sign younger free agents this offseason.