This app was mentioned in 6 comments, with an average of 1.17 upvotes
This is a good mobile option: https://play.google.com/store/apps/details?id=marcone.toddlerlock
In a few months to a year, go for Monkey Preschool Lunchbox.
Edit: go to the thrift store and buy a broken controller and/or keyboard for the child to play with.
I used Toddler Lock in the past, but it was many years ago.
Worked great. To exit it you have to press the four corners on a clockwise order.
It's been a long while since the last update, so I don't know if it still works with current Android versions.
I really liked this one:
https://play.google.com/store/apps/details?id=marcone.toddlerlock
Toddler Lock | 2.5 rating | Free | 1,000,000+ downloads | Search manually
> Child lock with colorful graphics and soothing sounds to keep your kids entertained without having to worry about them making calls or starting other apps. Teach your child shapes and colors. Optionally enables airplane mode ...
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toddler lock is good too, https://play.google.com/store/apps/details?id=marcone.toddlerlock&hl=en_US