I'm not sure where you are sourcing your information from that suggests meat is bad for you however I had trouble finding ANY information to support this opinion.

To the contrary, I was able to readily find many government & health links that suggest meat should be part of a healthy diet eg https://www.health.harvard.edu/staying-healthy/whats-the-beef-with-red-meat, https://www.nytimes.com/2019/09/30/health/red-meat-heart-cancer.html, and https://www.webmd.com/food-recipes/ss/slideshow-about-meat In addition, protein (lacking in a vegan diet), iodine, iron, zinc, & other vitamins & essential acids are found in meat, not just B12.

Keto is also very sustainable & healthy long term since most foods can be eaten. The only stipulation is foods moderate or high in carbs are avoided (this includes vegetables such as sweetcorn and potatoes). The only links I could find that keto may be bad for the kidneys is in those people that ALREADY have kidney disease, NOT that keto can cause it and again the evidence is inconclusive. I did however find a recent link that suggests a ketogenic diet can in fact improve kidney function https://perfectketo.com/ketosis-kidney/. Bear in mind I am referring to a keto diet in the true sense of the word with meat and dairy at its core.

Here is an example of someone who tried weight loss on a vegan 'keto' diet - https://blog.insidetracker.com/vegan-keto-body-changes. No doubt she was craving a good T-Bone steak by the time she threw in the towel. I know, because I too tried a vegan (mostly juice) diet and failed miserably at weight loss putting back on what I lost when it was too hard to continue with. This guy went further and made a movie on the subject https://www.rebootwithjoe.com/joes-films/ (and a pretty penny from sale of his movies). He lost weight. Then put it all back on again when he couldn't sustain it anymore (as did one of the morbidly obese cases he followed up with in his sequel to the main movie). I bet that first steak tasted good in his case too when he too finally could take no more food self-deprivation.

Here's some more good info on why meat should be part of a good keto diet https://www.dietdoctor.com/