I was forced to change UPS relatively recently (a few years ago) because the cheap but not bargain-basement PSU on my computer didn't work with the non-sine-wav

I was forced to change UPS relatively recently (a few years ago) because the cheap but not bargain-basement PSU on my computer didn't work with the non-sine-wave output of my UPS. Call them poorly-made if you like, but either I got unlucky or they're fairly common. Power supplies tend not to advertise their compatibility with non-sinewave power, but UPSes will certainly make it clear if they produce sinewave output. So the safe option is to get the UPS which gives the PSU what it's expecting.