How to convert a STOP message sent to an SMS provider into the "Do not SMS" privacy preference in CiviCRM?
It's probably possible to do via an extension, e.g. something similar to https://civicrm.org/extensions/auto-reply-twilio-sms
Otherwise there is a generic &quot;inbound&quot; function that handles incoming sms if the provider lets you set up a callback, e.g. twilio setup, and it's implemented in civi via this code and individual sms provider extensions can use it like this.
So it seems possible to implement something generic.