I hope all the things you mention never become mandatory some day because I currently use my phone for voice and text only. Sooner than later I plan to get rid of my phone all together. I'm gonna surprise the phone company and get a land line. That means any online service that uses SMS/text to verify me will fail.
If you're being serious, you're in for a rude awakening. POTS lines are dead and being replaced with VOIP and VoIP to pots modems on the premise. lots of cities have already started to grub the copper out and replaced it a long time ago with fiber.
I get what you are saying but POTS in my location is still copper. I know because I dug it up when putting in a cattle guard. I will have to splice it back together and run it somewhere other than under my driveway which I had paved. 811 marked it as disco/not-in-use. The telco accidentally leaked their plans to run fiber everywhere so I might wait for them to do that. If it ends up being VoIP then maybe I would still have SMS capability for poor mans 2FA? Maybe the competition will drive the cost of my existing fiber down. To userbinator's point the end result will be no more options to install applications. It would just be a phone. I would be back to good old fashioned NSA voice monitoring.
