RE: Further information on Basic Board and PSU for Original Prusa Enclosure (for Filtration unit and *custom* LED)
I don't have the URLs on hand, but I remember seeing in one of the articles about using the IO board to control the fan and light by connecting to the extension board. Seems the pins 3 and 4 can be used as active low switches paralleling the function of the switch buttons.
I'm wondering if the extra board on the CORE One is a result of the "smart box" project. Either planned to be released in the future as an enclosure add-on or fully redirected into the CORE One's accessory board with the "smart box" abandoned. I checked earlier today and that extra board hasn't yet been released to the store as a CORE One replacement part, but I expect it to land there eventually.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs