My daughter has a PEG, and though she doesn't have diabetes she is on a ketogenic diet for epilepsy, which is a high-fat low-carb low-protein diet that has a lot in common with my LCHF diet. So I'm answering from the point of view that low-carb is good for diabetes. Meat-based soup is a good option and can be thickened with double cream without clogging up the tube. There is a very useful product called Ketocal: it would be worth asking your dietician whether it could be prescribed for diabetes. Otherwise I think you can get it over the counter, but it's a bit expensive.