The ErgoDox had been developed by Dox and bpihany
on this board, with input from the community and the design released as Open Source. Most ErgoDoxen in the beginning were sold as DIY kits, and
several companies still sell loose PCBs and/or cases.
ErgoDox EZ is more or less that design pre-assembled with a fancier case and warranty.
A more recent clone (same layout but not 100% compatible with other parts) is the
Hot Dox. Everything on it comes soldered except switches, which fit in Kailh hotswapping-sockets. There is a
barebones option that I think would fit what you are looking for.
The ErgoDox is merely "columnar", not "
ortholinear": the columns are somewhat shifted against one-another; rows and columns are not orthogonal to one-another.
There are a few DIY keyboards that do look a lot like the ErgoDox except that they do have ortholinear alphanumeric keys, and you might have seen some of those somewhere too.
There are lots of other DIY columnar ergo keyboards out there that are more or less inspired by the ErgoDox and many of them are attempts to improve on the ErgoDox's thumb section: it has been criticised for having the thumb-keys too far out for small to medium-sized hands.
Learning to type on a columnar keyboard is easiest if you already know how to touch-type according to the method.