They identified the culprit! It was Ukrainian citizen, Volodymyr Z!
https://www.tagesschau.de/investigativ/ndr-wdr/nordstream-172.html
https://www.politico.eu/article/german-authorities-obtain-first-arrest-warrant-ukraine-nord-stream-bombing/
https://www.expressen.se/nyheter/varlden/ukrainske-dykaren-volodymyr-zhuravlov-44-efterlyst-for-sprangningen-av-nord-stream/

German authorities fingered three people as possible culprit for the sabotage of the Nord Stream pipelines, one of them the aforementioned not actually Zelensky, all three expert divers.
Apparently there is a yacht, called Andromeda, where traces of such explosive found, which could have been used. All three person is tied to the boat.
The German article provides a lot of details. A fun one:: the German prosecutor's last name is Rommel. Perhaps the whole thing is just some ML generated fantasy story.