Should be pretty basic, but it seems some Linux distros are moving away from the FHS. One thing I love about OpenBSD is that there’s no surprise where things end up. One thing you might consider covering is /usr/local.
I know this post is about Unix, but after I started using Ubuntu 6 years ago I have practically forgotten that /usr/local exists.
If all you’re using is the package manager, I can understand that. I still write a lot of code I use on my own box, and it all installs to /usr/local/, so I end up still using it a lot.
I’ve always wondered why (and when) people moved from putting home directories in /usr to putting home directories in /home