Hi - I have this one - not used it yet but see what you think. Ive use dthe combination of soya flour and ground almonds in other stuff and works okay for me. Here goes:-
Carbs
Rhubard stewed 150g/125ml or 1/2 cup 1.2
sweetener liquid to taste 0

topping
butter 25g/30ml 0r 2 Tbs 0
full fat soya flour 10g/30ml 0r 1/8 cup/2 Tbs 1.5
soya bran 25g/60ml or 1/4 cup 1.88
ground almonds 10g/25ml or 5 tsp 0.43
sweetener granular 2 1/2 tsp or 2 1/2 tsp 1.25

Servces 1 Total carb 6.26

Place rhubarb in ovenproof dish, adding sweentener to taste. mox dry ingredients in a bowl and rub in butter til resembles breadcrumbs. (If the mixture is too wet a little protein powder could be added) Sprinkle the crumble mixture on top of the rhubarb and bake at 200 c/Gas Mark 6/400 F for 20-25 minutes

To reduce the carb count to 2.75 use liquid sweetener instead of granular, substitute 40ml/1/6 cup vanilla protein powder, reduce the soya bran to 1T and increase th ground almond to 60ml/1/4 cup

You can also use other low carb fruit such as raspberries, blackberries, but alter the carb count accordingly

Hope it works out if you try it - like I said Ive not yet !!