Could you manage this yourself with a journal - style fitness tracker, like Massive?

https://f-droid.org/packages/com.massive/

Compound exercises like back / front squat and deadlift are also very good for your core

Abs are made in the kitchen. If you're looking for aesthetics, you need to look first at your nutrition. If you want equipment free core focused workouts, check out some Pilates or yoga apps or YouTube content.