Is a real dumb phone even possible? Not having apps and a touch screen doesn't make it dumb. Look at kai os for example or even symbian had apps just not nice appstores and nicer features. You still have arm cpus and running an os and apps.
A phone that only makes 4g calls with a 4g baseband os that is only capable of doing calls, now that would be a dumb phone but the cost would not be low.
It is possible, but it needs to connect to the phone network somehow and GSM chips/modules these days probably run Android inside anyway, so to have a really dumb phone means to have a separate CPU+memory+flash which doubles power usage and doesn't give any assurances that the GSM chip won't do MitM and fsck privacy of the phone anyway.
It's fairly easy to "enable" a "dumb mode" on a smart phone. iOS supports "guided access", where you can basically turn off everything, behind a passcode. There's also screen time, which lets you limit/disable anything, also behind a passcode.
But, this requires that someone else manages your phone.
There’s no platform SDK and everything you can do, you have to do through js. It’s pretty limiting compared to real binary applications running any sort of code (NDK)
A phone that only makes 4g calls with a 4g baseband os that is only capable of doing calls, now that would be a dumb phone but the cost would not be low.