It was a Ukrainian mission directed by the USA. Before you downvote do even a basic amount of research. There was a great finding recently that tracked down the who and the how. A chartered yacht with 6 Ukrainian special forces planted the charges and it's not an unknown anymore. They used fake passports, left out of Rostock Germany, and Germany traced it. They found the people via camera and entry. They found the yacht itself still with explosive residue on it.

https://www.washingtonpost.com/national-security/2023/06/06/nord-stream-pipeline-explosion-ukraine-russia/

https://apnews.com/article/nord-stream-pipeline-attack-russia-investigation-4b7cb8117f420985b0d887117eebd786