Not sure if this is relavent for you, but it seems to be similar to what you have implied.
After a colostomy, people wearing a colostomy bag may require adjustments to their diet. Their relationship with food may also change. Learn more here.
www.medicalnewstoday.com
The white bread and pasta tie in with low fibre. Certainly these items are counterproductive to diabetes care T2. So are root veg. This is not normal fare for our typical low carbers, but there probably some pick and mix items that could be suitable. The salt is LCHF compatible. Did the doc say this is long term strategy, or as is mentioned in the article I linked to, just while the surgery settles down?
The main problem you face is the low fat need. the F in LCHF stands for fat (not fibre) and it is what makes a low carb diet sustainable in the longer term. I wonder if this need for low fat is medical or is simply following the standard NHS nutritional advice. I know that gall bladder post op stipulates low fat too, but we have members doing LCHF without problem after their op.
Low fibre diets sound like a recioe for constipation. I have to ask Do you have a stoma, or was the surgery a resection? I see in the article that a lot of the recommended carbs are very processed. I wonder if the problem with fibre is just the bulk. Unfortunately I have no one to ask and rely on Dr Google, which is not necessarily fully reliable, and your question is one I have zero experience with.