Doesn't have to be SO. It can be a trusted friend who knows in advance that you may voice call them in a password recovery scenario (voice calls not via text).

Edit: regarding the "lack of availability" at the point of wanting to reset the password: the urgency of resetting passwords should be considered a lesser inconvenience than the risk of having lost control of your account through insecure 2FA.

(I am simply supporting my original brain storming thought through ... I am not married to this idea in any way or form. Just a thought.)