The article does not mention memory, and to me, that is the largest constraint on old systems when choosing an OS.
For a Minimal OS on an Old system, you can try NetBSD or OpenBSD, i386. Modern Browsers will be a no-go, but you will find NetBSD and OpenBSD very usable.
One note for OpenBSD, if you have less than say ~2 gig of memory, you may need to disable the kernel re-link. It will work, but will hammer the system. For NetBSD, I have it on a system with 512M and it works great.
Both fully are able to handle the 2038 issue on their i386 builds (32 bit) and has been able for a while. That is something you should be aware of for long term use.