Corollary - I did keto for just over a year while on a vegetarian diet with the main goal being weight loss. During that time I felt extremely energised and healthier. While not strictly vegan, my diet was basically the low-carb nuts, legumes, mushrooms, fruits, vegetables, eggs and cheeses. I did have to add a few supplements, otherwise I'd feel like utter shit, magnesium and electrolytes mainly had a significant effect on my mood. But otherwise it's the healthiest and most alert I've felt since I was a teenager.

People I mention this to assume the toughest challenge is variety but as I love to cook it wasn't too hard to make it interesting each day. The toughest challenge was convenience, you grab a coffee or a lunch with friends and there's very few places that cater for all. The second most challenging aspect was cooking meals for the family, as I am the main cook for my wife and kids who did not at all buy into a vegetarian diet let alone keto, but that again wasn't too bad since I could just cook a normal meal, scrape out the bits I can have and whip something up for me afterwards.

After about a year on that diet I ran a sub-1hr 12km charity race which isn't exactly a world record, but not bad for a 40-something always-recovering alcoholic with weight and mental health problems. I'd definitely recommend keto (with proper medical supervision) but... maybe not at the same time as trying to eat less meat.