The Belkin Omniguard family of UPSes can be made to work with nut by using the “gamatronic” driver. Neither the belkin nor belkinunv drivers work, bu gamatronic seems to work just fine. I guessed this based on some random post I did find on the internet from someone saying they’d forward-ported something they called the SEC drive from an older nut release; grepping the current nut tree’s source code I found some SEC_xyz defines in the gamatronic driver, so I just tried that, and it worked.