We got a tablet for him about 3. It was only used for long road trips and even then just to watch 1 movie. He's 5 now and he gets 1 hour of screen time on it each weekday. However it's not a free for all situation. He has to spend about 30 minutes in an educational app first and then he's allowed to watch videos from a curated list.

I can see a huge difference in his behavior when he gets "too much" screen time. This is what works for us and every kid is different. I would recommend limiting screen time as much as possible without putting them too outside the social norms. At 3 that isn't a concern but at 5 he does have friends now and it's healthy for them to be able to bond over things they've both seen.