A colleague from a different team often spends hours discussing his personal projects with us during work hours. These projects, which are somewhat related to our field, become a frequent topic of conversation, especially when he seeks advice. Unfortunately, once we engage, he regularly updates us on his progress the next days/weeks.
The issue is, he doesn't grasp that I'm not the least bit interested in what he's sharing, despite my hints—I've cut conversations short, looked away, went on with my tasks while he talks etc... He always starts speaking and even after I express my busyness, he generally switches to another colleague, then leaves the room and eventually comes back to me asking if now's a better time, starting his talk before I even answer.
I don't know how to deal with this situation: I want to express my disinterest in his projects, but I hesitate because while I have no business with him, we never know what the future will be made of.
I'm also reluctant to involve his manager, as I don't wish to cause him trouble, especially if his manager is either approving or oblivious to his focus on personal endeavors during work hours.