None referred to the list of accusations. It doesn't make sense for Russia, NATO countries announced it and ruled (just now) it was sabotage (while they could h

None referred to the list of accusations. It doesn't make sense for Russia, NATO countries announced it and ruled (just now) it was sabotage (while they could have kept it hidden), and for Ukraine it would be really foolish if it was found out at a bad time, because it can turn public support. So there's no sensible candidate (with the current state of knowledge).