How would the UPS in this case communicate with the server? Do you have a specific UPS in mind, or a general question?
In essence, HexOS runs Linux and TrueNAS. If the UPS has a way to send this information to the server in some way, an application could probably be built for this. From a quick look around HexOS apps I couldn't find anything, but I would guess this would be solvable on the TrueNAS side, of course, depending on the UPS.