@andrelam, do you assume that a “Clean flash” will be necessary or could it be sufficient that e. g. only system Dalvik cache need to be deleted?
With the already installed TWRP Recovery we can make a device-dependent backup (Nandroid-Backup) and pull this data over to the PC or store it on an external mircroSD card.
My robust Samsung Galaxy S5 “klte” has already accepted some experiments and also swallowed the upgrade to n-9-pie without any problems.
What are the names of the “Some devices” that don’t want to boot anymore?