1 pointThis one: https://support.hpe.com/hpsc/swd/public/detail?swItemId=MTX_e9bfdf20809a426cb16ef9cd81#tab2 What file have you been trying to install from iLo?
1 pointProbably wasn't designed with the right power supply and cooling. Might also affect noise and EMI emissions. Otherwise, really stupid they didn't provide the sheet metal and power connection to support another drive, but the focus on the UDM Pro is rack mount form factor, not being a total all-in-one solution as they didn't include any PoE ports which is also stupid unless again power supply and cooling would push the cost higher and complicate the design from what they have.
1 pointThe OS booting and BIOS update are unrelated things. Just flash the latest BIOS using iLO and then start to think about OS boot.
1 pointHave you tried to update the BIOS with a bootable USB and not use iLo?
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