Ubuntu is not intended for old hardware. It is intended to be an easy-to-use distribution with decent adaptability to server and desktop use. It's not bleeding edge, but it's not all the way over in the "staid enterprise" category, either.
The 24.04 release is the next release to get long-term support (5 years; commercial plans of 10 years). If you're going to stick this on a computer to run a long time, you care what it looks like (LTS releases come out every 2 years), so you might be running a beta to give feedback.