Answer: Pysllium husk is keto, as it's almost entirely fiber.
Psyllium is a natural fiber that has been shown to treat digestive issues such as constipation, as well as improve heart health.
A single teaspoon of psyllium husk contains 4 g of total carbs, but this is entirely from fiber, so it's 0 g net carbs. It contains almost zero proteins or fats, so it won't help you hit your macros, but you can take some psyllium if you want a bit more fiber in your diet.
The powdered fiber supplement Metamucil is primarily pysllium husk, though it is not keto due to its sweeteners.