https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0284132

To study health outcomes in cats fed vegan diets compared to those fed meat, we surveyed 1,418 cat guardians, asking about one cat living with them, for at least one year. Among 1,380 respondents involved in cat diet decision-making, health and nutrition was the factor considered most important. 1,369 respondents provided information relating to a single cat fed a meat-based (1,242–91%) or vegan (127–9%) diet for at least a year. We examined seven general indicators of illness. After controlling for age, sex, neutering status and primary location via regression models, the following risk reductions were associated with a vegan diet for average cats: increased veterinary visits– 7.3% reduction, medication use– 14.9% reduction, progression onto therapeutic diet– 54.7% reduction, reported veterinary assessment of being unwell– 3.6% reduction, reported veterinary assessment of more severe illness– 7.6% reduction, guardian opinion of more severe illness– 22.8% reduction. Additionally, the number of health disorders per unwell cat decreased by 15.5%. No reductions were statistically significant. We also examined the prevalence of 22 specific health disorders, using reported veterinary assessments. Forty two percent of cats fed meat, and 37% of those fed vegan diets suffered from at least one disorder. Of these 22 disorders, 15 were most common in cats fed meat, and seven in cats fed vegan diets. Only one difference was statistically significant. Considering these results overall, cats fed vegan diets tended to be healthier than cats fed meat-based diets. This trend was clear and consistent.

Not to be a stick in the mud here, but... what? How on earth does "cats fed vegan diets tended to be healthier than cats fed meat-based diets" follow after "considering these results overall"? You mean the results that weren't statistically significant? Those results? And that one statistically significant disease difference? It was for kidney problems, and the vegan cats had more problems than the non-vegan ones (table 6).

If there's a case for feeding cats a vegan diet, this ain't it.