As all things digital. Everything can be hacked and it’s usually a lot easier than you think. There’s two big areas that create issues with all these technologies: one is the deliberate and sometimes hidden misuse by the companies who produce the devices, the other is the ease for third parties to hack those. Oh and btw. If somebody hits you unconscious can they still use your face to unlock the phone? If you get a skin disease that disfigures you, will you be locked out of it?
But maybe the security and privacy concerns are actually exaggerated, the real question might be: why in the first place? I think we lost sight of this question.
Getting out of smartphone dependence is… well… actually just a matter of just doing it. I thought it would be hard, but then I just stopped using the smartphone for anything that wasn’t essential and in a relatively short time it was just as if it wasn’t there, except for the stuff that mattered. So in the end it’s not using a dumb phone that will free you from the smartphone, it’s just you and once you’ve done it, you can just keep using the smartphone because it won’t matter anymore.
Now the funny thing is: I ended up with a 800€ phone to do the same things I could do with a 24€ Nokia thing. Which makes me wonder, why did I shed out so much money in the first place? Could have bought me a couple of modules instead 
The other thing is: I still have an old Nokia Dumbphone and it’s over 10 years old.
It’s made of cheap plastic, lousy mechanics, probably super shaky SMD components… butit’s generally been in heavy use for at least 50% of that time and it still runs perfectly. In the meantime I went through 3 iPhones and none of them lasted more than 2-3 years. They all suffered of failing hardware (buttons not working anymore, wifi getting fried, etc.), quickly degrading batteries and most prominently degrading performance with every firmware update (when I noticed that I stopped updating and in fact my last iPhone lasted longest).
So I’m on the lookout as well… but I really don’t know what I should do, since choosing a new phone has become such a hassle and I have better things to do (like writing really long posts about it… I know). So I guess I’ll just stick with the Nokia thing until that dies as well and then see what I can find.