Extruded aluminum of that type is insanely stable and easy enough to build for a reasonably handy person.

You only need a cheap cutoff saw and a drill, or you can order pre-cut and ore-drilled pieces to order.

There are a number of makers of extruded aluminum building systems, basically tinkertoys for adults. I have personal experience using 80/20 and the Tslots brands. They are functionally identical.

I have used it to build stands for heavy equipment like ultra-cold freezers for labs. It is more than sufficient for any server racking.