You assume the OS package manager I happen to be using even has packages for some of the libraries I want to use.

Or for that matter, that the ones they do have are compatible with packages that comes from other places. I've seen language libraries be restructured when OS packagers got hold of them. That wasn't pretty.

Nothing about their post indicated they assumed that.

They offered two options, so you can go do the other one if it doesn't work for you.