Perhaps Huel offers a keto product in the future - as there seems to be enough demand for it. I know lots of people who believe in low-carb.
As far as I know there seem to be differences in low-carb diets, though. Everybody defines a different upper limit. For ketosis I think the cutoff is 5g per day, but there are also other, less strict strategies where people have a higher amount of carbs. Perhaps you just need to find the right cutoff value for you, and maybe this does not even have to be as low as just 5g carbs daily.
If you are craving sweet flavours it may help to use artificial sweeteners or flavour drops - they are sucralose based and calorie free.