I’ve been using mains filtering and conditioning because I had my doubts about the quality of the waveform coming out of a UPS, and also because a bit of extra lightning protection can't hurt. I’m now using a Belkin PureAV 8-mains block on the output of the UPS.
[and that’s not all as there’s a whole lot of additional totally over the top mains defence stuff in there too, as an experiment. With >63 ds attn and living on too of a hill 400ft up above the sea in quite a storm exposed region I’m simply trying to improve my chances for better signal quality as far as humanly possible, while at the same time attacking the wrong problem by protecting mains as much as I can whereas of course it is the copper DSL link that is the real storm threat here.]