So... start with a dmesg from both. Run the dmesg through "diff -u". Are they as "identical" as you think? Little things like ROM revisions matter.
And make sure nothing other than the UPS is plugged in. Even in the fragment of dmesg that you sent, one finds it at usb3 and the other at usb6, so that is a difference. Either you have some other USB stuff in one that's not in the other, or the machines are wired slightly differently...
Two mobos having the same model number never proves they are *identical*. Unless you're in an expensive realm like war contractors, those two mobos are certainly not guaranteed to be identical down to the chip level. Mobo makers often substitute a cheaper part, or a part from a different supplier, in the middle of a production run. It "works" because Microsoft is given this info and/or the vendor makes drivers available to them, but non-Windows OSes suffer. That is one faint possibility here, but bios settings, having other stuff plugged in, etc as mentioned are stronger candidates.
If the dmesgs confirm your statement that they are the same, swap the UPSs between machines, and the cables between machines. Does the problem follow the computer, the cable, or the UPS? If it follows the computer, look in the BIOS setup, screen by screen, on both machines. Something is different. you need to find it. Especially since you provided no information for us to work from. 🙂
