Wat? No. We don't. The article itself doesn't even make that claim. First, it's reported to be from anonymous sources in the US intelligence community. That's a pretty substantial pool of potential sources whose credibility cannot be ascertained by the reader. Second, it says the evidence only "suggests" it was a Pro-Ukrainian group. Based solely on this limited report, we absolutely do NOT know that this excludes Russia. Lastly, it also states that officials who have been briefed on the findings are divided on how much weight to put on the info, which naturally means some of them don't believe it to be credible.
I would also question the writer as they claim 1) Ukraine had a lot of incentive to see the pipeline destroyed, and 2) Russia had no motive to do so. You can quibble about the first point, but there's no debate the second is untrue.