First: mmastrac was explicitly talking about rooting Android devices via an exploit. Since as far as I know there are Android devices available that can be root

First: mmastrac was explicitly talking about rooting Android devices via an exploit. Since as far as I know there are Android devices available that can be rooted on your own, buying one where an exploit is necessary is a conscious decision by people who don't care about such rooting. So your argument is off my point. This said: To my knowledge for some mobile phones using a TI Calypso chip, one can flash a free firmware (OsmocomBB): > https://osmocom.org/projects/baseband/wiki/Phones https://osmocom.org/projects/baseband/wiki/Phones