To my New Zealand (British English) ears, “my good man” is an old-fashioned, English phrase. Everywhere in the English-speaking world, nowadays, it would mostly be used only in a humorous way. :)

To my American ears, “my good man” is an old-fashioned, British phrase. In America nowadays, it would mostly be used only in a humorous way.

I would see it as an old fashioned, condescending form of address. It would either be a joke or imply that the speaker considered themself superior to the other person

If you are friends with someone, you could call them that. It can contain an element of humor, or it could just be close friends talking to one another.

Thank you for the comment. Actually this is a scene where an aristocrat talks to a local peasant from a Russian book written in the 19th century. (translated by a British translator) So, you hit the nail on the head when you said old-fashioned. I wasn't sure if it would sound from a contemporary perspective.