We as regular citizens have limited info, really we don't know what's going on. But don't assume it definitely isn't Russia because of whatever reason that happens to seem plausible to you.
There's a very real possibility that the actual goal of this entire mess is/was for Putin to get into the history textbooks as one of the great Russian leaders before he dies from cancer (or whatever it is that he has).
On the other side, Ukraine destroying the pipeline and making sure EU members don't give it to Russia in order to restore the flow of gas makes pretty good sense.. as long as you don't care about the EU citizens.
Argument in favor: It's obvious sabotage. If Ukraine, the USA, et al did it, it would have been in their interests to make it look less deliberate.
1. To do the repair EU needs to lift sanctions
2. Gas prices spiked = short term monetary gain
3. Not so subtle message: hey Norway-Poland nice pipeline you opened here today, you should hope that nothing bad can happen to it.
Russia looses massive leverage by no longer being able to deliver gas, even if they wanted to.
Prior to this, if the public got cold enough, they could tell their government "forget Ukraine, we need gas. Go agree to get it or we will vote you out ASAP". Now.... There's no point in settling anything with Russia, since you're not going to get their gas anyway.