By the time they reach retirement age, Raspberry Pi will be back in stock

Might not be the most straightforward way, but not so far fetched either. I personally got interesting by writing small programs on a HP48, I’d imagine people getting hooked either from small algorithmic games, or writing shortcuts/automations.

Coding is not allowed.

While I am not a child, I use my smartphone to read through a lot of (e)books on my daily 2h+ commute and it helps me a lot to avoid awkward staring contest with random strangers. I always re-stock books from O'Reilly and No-Starch press my device over weekends for the next week to read.

In summary, my smartphone helps me 10h+ reading while avoiding equal amount of awkward moments with strangers.

I agree, but it's worth noting that scratch can be used on a phone. Wonder Workshop is an example.