Type 2 for 12 years and im on long acting insuling (not the type 1 stuff at each meal, just once a night)
It's actually really simple and took me ages to work it out myself then the crap old school stuff they teach you at the clinic/docotrs/hospital.
You can do it two ways:
1. Eat clean and reduce carbohydrate portions to be the smallest (150-250g a day max) part of the plate/meal. Eat lots of green leaf stuff and meat with fat is totally fine and will help fill you up. Obviously cut out all sugars (including alcohol sugars! look up hidden sugars)
2. Go the very low carb or Keto approcach, I lost 18kg doing this alone in 8 weeks, put some of it back on sliding off the wagon with carbo binges.
At the moment I just do low-effort keto up to 1500cal a day, basically I avoid all carbs (minus net fibre as that doesn't count) and max I get a day is 10-15g. This alone makes my bloods go to about 5-7mmol throughout the day which is the normal blood sugar bracket and thats WITHOUT having to take my insulin. I still take my insulin now and then if I have the blow outs, but so far it's all food.
Also just to remind you, exercise helps reduce weight but it's more about the food, exercise should be treated for it's health benefits like blood flow, moving joints and mental health benefits, don't hit a gym and stress out on trying to lose weight, food alone will do that (watched my boss drop from 140 to 90 from diet alone)