I am working on an SRS based early literacy acquisition webapp: https://letterspractice.com

The app has recently moved into production, so I'd encourage anyone with verbal but pre-literate kids to check it out.

The basic pitch is high efficiency acquisition of the highest yield phonetic mapping skills, and nothing else. I myself am something of a screen-time zealot and very wary of applying engagement mind hacks against kids. The narrow focus allows for good progress on a very modest schedule (recommended cap at n minutes per day for n years old, n >= 2). I defer the social and cultural aspects of learning to read entirely to parents.

It is mostly intended for parent-child co-use, although kids with a bit of experience can drive many of their own sessions most of the time.