I liked this article a lot. (For those who didn't read the original paper, the acceleration observed by Oumuamua would be consistent with it being a discarded light sail from an alien civilization that had been drifting in space for millions of years.)
Is it particularly likely? No, extraordinary claims require extraordinary proof. But it genuinely cannot be ruled out. And a priori, I'd have expected the first clearly extrasolar object seen in our solar system be be a garden variety comet (we know those get ejected from our own solar system all the time), not a weird long rod and or tumbling thin film. And even if it was an artifact of an alien civilization, we'll never be able to find it again or know for certain. *shrug* I like that the universe having a little more mystery in it than it did a year ago.
If it was an active spaceship, I'd assume it'd wouldn't have been tumbling. Light sails don't work as a method of propulsion if they don't stay facing in the same direction.
For a more science focused and less sensationalistic view of the analysis in the preprint which triggered all the popular press articles:
https://www.centauri-dreams.org/2018/10/29/on-oumuamua-thin-films-and-lightsails/And the preprint itself:
https://arxiv.org/pdf/1810.11490.pdf
