Perhaps there’s a B2C offering to be made here. An SMS proxy, forwarding 2FA codes to people without SMS.
It would require a lot of trust.
Similar and related discussions on this post:
https://news.ycombinator.com/item?id=43976359
Daito does this:
https://www.daito.io/2fa-via-sms/
Daito does this:
https://www.daito.io/2fa-via-sms/