I didn’t experience any health problems and fiber is explicitly encouraged as a way to get unavoidable carbs down. Like I said, you have to avoid the fad keto stuff that I luckily got in before it took off. Sounds like most people are only going off the dangerous/nonsensical fad keto stuff that all diets are subject to with enough popularity. Basic rule of thumb is if someone wants you to buy anything more than just food (supplement, pills, etc) stay away. Keto (the actual dietary principle) is just based on a different distribution of macronutrients when achieving your caloric deficit. I wasn’t trying to disparage IF, just offering the comment OP another option in his failed diet search.

You need fiber, friend. You. Need. Fiber.

Citation please. As far as I've read fibre does two things:

1. Anti-nutrient, when people eat terrible food fibre blunts it so it isn't as terrible by preventing some of the bad food absorption

2. Fibre is digested by the gut into short-chain fatty acids (SCA / BHB) which get absorbed through the gut, and has a boost to health in the area of absorption. However, in a ketogenic context the liver is making Ketones (BHB) all the time which gets deposited into the blood stream being available to the entire body including the gut... so this benefit is only seen in a carbohydrate metabolism, and not in keto.