3 months post DIEP flap reconstructive surgery I worked with a personal trainer who was level 4 cancer rehabilitation qualified. I'd definitely recommend seeking someone out to help you curate an exercise plan.
The exercises I was recommended to do were: planks, squat + reach, ledge presses, deep breathing, bridges, crunches (on back and face down), crunches to knees, cat stretch, child's pose and lots of stretching. I usually did between 10-12 reps x 2. I hope this gives you some good ideas!