My, admittedly layman, understanding is that it was a very difficult thing to do from a technical perspective. And that there are very few countries that have technical capabilities to accomplish this. Ukraine is not one of them.
Why would you conclude this where every intelligence and law enforcement agency that has looked into it and published a report has found the opposite?
Do you have a basis to conclude that "every intelligence and law enforcement agency that has looked into it and published a report has found the opposite"? You exhaustively went through all Western intelligence and law enforcement agencies and read their reports? So you are quoting other news articles/interviews. Apparently their views differed. Ok.