Just been perusing the HDBB2 breakout board from CNC Drive. This appears to be nothing more than an up-market version of the cheap Chinese parallel port breakout board with opto-coupled inputs and a number of improved features. The company advertise this board as suitable for use with LinuxCNC direct from an old PC's parallel port as well as with CNC Drive's own products. Since this board is a necessary add-on to the UC400ETH Ethernet controller anyway, it might make a good starting buy for a budget build with the option to upgrade at a later date.
Has anybody used one of these in this way?

https://www.benl.ebay.be/itm/HDBB2-b...-/121287188690