Yes, the ReMix was a general purpose board that was capable of driving 3D Printers. This was back in 2016-2017. We have since “focused” specifically on laser cutter control and products.
Lots of people seem to like Marlin2 and I sent boards to the devs so they should be supported, but it’s not something I have direct experience with. I use Smoothieware on my printers still.
If you go to https://cohesion3d.freshdesk.com/support/solutions/5000167052 you will find the old documentation portal that has a bunch of info for the remix board, in particular the Getting Started page and pinout diagram
The Smoothieware also has a lot of useful documentation on configuration
I’d recommend using Smoothie to start with until everything is configured and working to your liking, then decide how you want to proceed.