The proliferation of popular science articles about "Viking cats" seems to come stem from a single conference: The 7th International Symposium on Biomolecular Archaeology, hosted in Oxford in 2016. This paper was published in 2017 as "The paleogenetics of cat dispersal in the ancient world," available here

It was claimed there, using genetic testing on mitochondrial DNA from archaeological sites of cats from the Mesolithic to modernity, to test the influence of various subspecies of cat.

The published article is worth quoting at length.

North of the Alps, domestic cats appeared soon after the Roman conquest, yet remained absent outside the Roman territory until Late Antiquity. In medieval times it was compulsory for seafarers to have cats onboard their ships, leading to their dispersal across routes of trade and warfare. This evidence explains, for example, the presence of the Egyptian lineage IV-C1 at the Viking port of Ralswiek (7–11th century AD). The expansion of the domestic cat may have been fostered by a diversification in their cultural usage, which in Medieval Europe included the trade of domestic cat pelts as cloth items. Spread of the black rat (Rattus rattus) and house mouse (Mus musculus) by sea routes as early as the Iron age, documented by zooarchaeological and genetic data, probably also encouraged cat dispersal for the control of these new pests.

As part of the evidence for the claim of mandated cats on ships, the team cites "Untersuchungen an Skelettresten von Katzen aus Haithabu," which is to say "the investigation of Cat Skeletons in Haithabu" or the Viking Age town of Hedeby. Unfortunately, 1) this book is out of print and has never been digitized and 2) even if I could get a copy, I don't read German well at all, so I can't trace the research farther back to see where that claim comes from and whether it applies to the Viking Age as well. That being said, there is some evidence for it in Irish law codes, translated in Kevin Murray's "Catslechta and Other Medieval Legal Material Relating to Cats," Celtica 25 (2007). He looks at the term Baircne, which either means a female cat or a cat owned by a woman, and all the law codes have entries related to it arriving on a ship.

Additionally, cats must have made it to Iceland before the 13th century; trollish cats appear in Vatnsdæla saga and are remarkable not because they are cats, though 20 of them appears to be excessive, but because they are "trylldir" and therefore dangerous (Ármann Jakobsson, "The Big Black Cats of Vatnsdalr and Other Trolls: Talking about shapeshifting in medieval Iceland," 2018).

So, it is at least plausible, even though there is little direct evidence to confirm it in my research, that Norse sailors had cats on their ships, including when they went on raids.

Postscript: All that being said, the popular science articles, by citing such evidence as the cats that Snorri claims drew Freyja's chariot, imply that Norse people viewed cats as sacred and took them with even to battle. There is no evidence to support this, as far as I can tell; no accounts of battle, either from contemporary Continental sources or later Norse sources, indicate that cats were present on battlefields; they aren't an archetypal beast of battle, like ravens, eagles, and wolves were.