Fresh install on Lumia 650, most recent OS version 1703. (Build 10.0.15063.540)
MSA/Xbox account under family safety
(same account plays windows 10 edition without problems)
Language German, Region Germany
Game installed on on-board flash
Game shows white Mojang splash screen for about 21 seconds, then exits, no error message.
Phone rebooted, no change
wifi on/off, no change
flight mode, no change
deleted game, reinstalled, no change
changed family safety setting to adult, no change.