People on plant-based diets tend not to eat a ton of plant-based meats, and lower income people are esspecially less likely to be relying on them because of cost?

I don’t follow what you are saying about not being applicable to the US, and UK. Those countries are the modeling study most applies to and shows lower costs?

Additionally it’s worth mentining if we look at other data, lower-income people are most likely to be vegan and vegetarian

Meanwhile, lower-income Americans (7%) are about twice as likely as middle- (4%) and upper-income (3%) Americans to be vegetarians . https://news.gallup.com/poll/510038/identify-vegetarian-vegan.aspx

I know of people that do even vegan keto. There’s actually a decently large subreddit for it. There are resources out there if you feel inclined to do so

I’d always caution people about keto in general though, esspecially for meat heavy keto. A lot of the discussion around it is not always the most scientific

Much of what people may be observing from keto is likely not as much due to carb limits, but from watching food closer. On most diets, people tend to report stuff like weight loss because they’re more aware of what they eat. Or in other cases, changing foods around accidentally ends up avoiding a very specific food sensitivity. For instance you’ll find lots of similar observations from a whole-foods plant-based diet

If it’s not being done for reasons like epilepsy, Keto overall has some not so great long term health impacts that people tend to gloss over. Though much of that research finding more negative outcomes look at people doing so with a meat heavy diet. Ranging from bone health to kidney damage. If I remember correctly, the more limited research about vegan keto has found better results, but I’d still advise caution in general

TLDR; yes it’s possible and there are people that do it, but just be careful about keto in general because it’s got some long term impacts that aren’t so great