I agree with routerdriver about LinuxCNC. If you're building a basic machine then it's easy to install and set up using the included wizards. No delving into the depths of Linux complexity at all.

If you have not bought any rails already then I think most people here would advise using the Hi-Win style linear guide rails in 15mm or 20mm sizes rather than supported round rails because of their greater rigidity but they are more expensive. This link shows the sort of thing.
https://bstmotion.aliexpress.com/sto...d_324926.1_2_4