New to here but no t my first rodeo.

I am a septuagenarian and I’ve been at this since 1975. Lost 100 lbs in a year once. 60, 70, 80 lbs, no problem. Always have gained it back. My daily goal of is less than 1200 calories. Anywhere near that and I start gaining. The app keeps yelling at me to eat more or it won’t let me close out the diary or announce any progress. I left Noom because they accused me of lying and fudging my meal input. I’m not expecting anything, just a place to track my calories.