Re: vegan cats, they actually can do well on a properly planned/supplemented vegan diet, although more research is needed

www.ncbi.nlm.nih.gov/pmc/articles/PMC9860667/

“However, there is little evidence of adverse effects arising in dogs and cats on vegan diets. In addition, some of the evidence on adverse health impacts is contradicted in other studies. Additionally, there is some evidence of benefits, particularly arising from guardians’ perceptions of the diets. Given the lack of large population-based studies, a cautious approach is recommended. If guardians wish to implement a vegan diet, it is recommended that commercial foods are used.”