Atkins/Keto/high protein diet for the rest of your life after bariatric surgery is old school nutrition nonsense. FYI most doctors only need to take 1 semester of nutrition classes and that was back when they were in in undergrad or med school. A lot has changed since then. As long as you eat a well-planned, plant-based diet (this applies to non-bariatric patients as well) you will thrive. I'd say success after bariatric surgery is more about using the time where you have restriction to learn better habits and ditch your addiction to empty calorie dense carbs like white breads, pasta, white sugar, etc. than anything else. You will eventually be able to eat normal portions of food so breaking bad habits is key. If you continue to eat a SAD diet and the crap that made you fat in the first place, even if just less of it, you will eventually experience regain.
Immediately after surgery (first 1-4 weeks), you will be drinking/ eating very low cal in the ballpark of 500-800 calories. You will be weak some days because of lack of calories, not lack of protein. It takes years to become protein deficient! Then you'll probably be around 800-1000 until 8-12 weeks., 1000 - 1200 for a good while after that. I hovered around 1000 - 1200 for my first year post surgery.
Look up Dr. Garth Davis, he is a bariatric surgeon who advocated a whole foods plant-based diet. I also like Dr. Matthew Weiner - he has a number of videos on Youtube, both have Facebook pages and groups to help you.