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

I would separate a program as such and an app to follow a program. I personally use gymrun, whatever m program is. I like its wearos support.

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.