In case it's useful, here's the exact system I have: https://everymac.com/systems/apple/powermac_g4/specs/powermac_g4_350.html
It's running Open Firmware 3.1.1 (1.2f2 BootROM). This is what it came with, and I was unable to find any upgrades online for this particular model. -- Ben Westover
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