Need some advise in managing a lazy counterpart

I’m a fairly new manager in a multinational company, my counterpart had been here for quite a while. He’s a bit lazy, not so smart and is known to keep delegating all his tasks to his direct reports (we manage per region in one dept). We recently moved to a new software, and during the transition stage he was nowhere to be found, since I was worried about the team I lead the necessary trainings, and set up all the needed access rights in preparation for the transition. He only needed to attend those trainings (which he didn’t) and read all of my email announcements (which seems like he doesn’t).

Now this manager had a 1:1 with our boss complaining that he feels left out, and that he is not able to follow on what’s happening with the transition. I also feel like his relationship with our boss stems a little bit deeper because despite of his non appearance my boss called me out to say that I should always keep him in the know of what’s happening. I did reason out that all everyone needs to know are posted in our group chats and email blasts but it really took me off guard. I’m two months away from probation. How do I handle this? His direct reports are also reaching out to me for help but our boss turns the blind eye and sees him as the golden boy still.