I grew up in an odd era, in which when you wanted someone to play with, you walked down the block (or biked if it was a couple blocks) over to a friend’s house and knocked on their door to ask some scary adult person if Johnny could come out and play. As dangerous as such a practice is in our more progressive age, in which we clearly know that children’s playtime needs to be rigidly scheduled in what are detestably called “play dates”, nevertheless, I personally parent my own children in a manner quite similar to my own upbringing. When one of them is bored, I suggest biking over to a friend’s house to see if they are available, all on their own.
Strangely, none of my children are dead yet. And they also function independently pretty well in a pinch.