This has been discussed under a couple of topics in the forum.
Here is one:
“Four Conditions for Attaining Sōtapanna Magga/Phala”
The main conclusions are:
1. The Sotapanna Anugami stage can be reached by reading/listening.
2. The Sotapanna phala moment (transition from a Sotapanna Anugami to a Sotapanna) happens while listening to a discourse by a Noble Person (Ariya).
– “Saddamma savana” or “listening to the correct Dhamma” is what is given as a requirement in the Tipitaka.
– Of course, reading was not widely available at the time of the Buddha.