Should be OSX 10.5.8 if anyone is curious. Which can be used all the way back to the 2002 quicksilver G4’s that ran 867 MHz processors. Which is dumb, the dual cpu 800 MHz were limited to 10.4.11 and couldn’t upgrade. But at that point they were quite dated anyways so it doesn’t matter that much.
PS1. Unless mouse and keyboard counts….