I don't think any can be conclusively ruled out, but if we start to weight each candidate by things such as

* motive(am I gaining/losing leverage by this?),

* ability (can I actually do/help/enable this action?)

* consequence (can I get away with it? Can I muddle it and make people get along with it?)

* context (a war is going on, but so is internal politics; does my context push me for this action?)

I think probably more than half could be reasonably ruled out, depending on how each of those were weighted. And we could probably reason about the accomplices too

The issue here is that the state with the most motive (Ukraine) is one that most are agreed did not have the opportunity to actually conduct the attack. Nobody else has a strong motive. The US had already achieved what it could have hoped to achieve months before the pipeline explosion. Russia's plausible motive assumes a certain amount of strategic insanity mixed with thuggery. Everybody else's motive more or less rests on making a political statement that they haven't been making in public.

I'm not so sure Ukraine didn't have the means. See "Royal Navy divers train Ukrainians to hunt for mines with underwater drones" for example https://www.royalnavy.mod.uk/news-and-latest-activity/news/2...

We've seen Ukranian drones drop grenades on tanks and attack ships at Sevastopol so it wouldn't seem that unlikely.

Also the Russians said it was Royal Navy + Ukranians https://www.reuters.com/world/europe/russia-says-british-nav... As a Brit I'd like to think so.

> Can any of these be conclusively ruled out?

Of course not. It's a fallacy to think it is possible.

Even in the case where someone claims to have been the party that did it and produced documentary evidence showing it the political environment dictates that other parties will claim it is fake or a false flag.

Might as well also consider the possibility that they weren't damaged at all then too.

Rule out Gazprom and Transneft, because they are not independent in any way. If you think that there are independent oligarchs that can do such thing, then I have to inform you there are no oligarchs after beginning of 00s in Russia. Sure there are rich people who "own" big companies, but most of them are Putin's friends and others won't even think about anything like "independence". Putin can say one word and these people (like anyone in Russia) will go to jail for 15 years, die strange death or would have to leave country (if they are able to do this fast enough). Berezovskiy and Hodorkovskiy examples were enough for everyone to understand that oligarchy is gone.

Moreover Gazprom and Transneft are state-owned.