It’s wild because in a lot of cases the FDA does have jurisdiction over the apps, they just choose not to check them.

My understanding is that you’re not going to find a self hosted solution that makes use of SMS (not counting email to SMS gateways) because sending SMS programmatically requires a SMS gateway those aren’t cheap (think of Twilio). You can find many options for app-based notifications (push notifications usually) and email-based notifications as a workaround.