I have the impression that many forum members count net carbs, and that it works for them. But there is also a contingent of members who either started by counting total carbohydrate intake or switched to total when using the net count didn’t work for them.
Dr. Stephen Phinney, one of the pioneers of keto research, says he tells patients of Virta Health to stick to a limit of 50 g total, in the hopes that they will end up under 20 g net. But his advice on the practicalities of a keto diet is that, if people feel stuck on keto, the first thing to try is to limit carb intake even further. The second thing to try, he says, is to eat more fat. And he says that on no account should the person eat more carbohydrate.
Dr. Eric Westman, another pioneer, and director of a well-known obesity clinic at Duke University, tells his patients that, while they can count net carbs, limiting themselves to a total of 20 g/day is the “prescription strength” version of the diet. He finds that to be easier and simpler for the patients. Dr. Westman also, in a lecture at Ketofest a few years ago, said there was starting to be evidence showing that fibre might not be as indigestible as as hitherto been believed. (But I don’t recall that he cited any particular study that we could follow up on.)
The reality is, of course, that everyone’s carb threshold is different, depending on their degree of sensitivity or resistance to insulin. The story going around the forums when I joined in 2017 was that @carl and @richard really wanted to tell people to eat no carbohydrate at all, but were afraid it would scare off people who could really benefit from a ketogenic diet. So they picked a limit of 20 g/day, which should be low enough to work for everyone but the most insulin-resistant. They leave the choice of net or total up to the individual.
All good at all times!!!