This app was mentioned in 2 comments, with an average of 1.00 upvote
My daughter (almost 3) has been playing with ABC Kids - Tracing and Phonics from RV AppStudio. It is free, has no ads, and doesn't request any permissions. It's on the Google Play Store, I don't know if it's on iPhone.
https://play.google.com/store/apps/details?id=com.rvappstudios.abc_kids_toddler_tracing_phonics