im having a similar problem, after full ota update (2.6gb) from rooted 10.0.8 im losing mobile network (two SIM icon, greyed out, with a slash sign over it and no baseband infromation) after booting/flashing this boot, even creating mine. Mobile network restores after returning to stock. any clue? Im on 10.0.9.HD65AA
im autoanswering myself, just to let somebody else know if having the same issue:
looks like OOS Native Caller Recorder 8.0 (magisk module) was causing phone app to crash.
disabled, reboot, removed, reboot, updated to 9.1, reboot, problem solved.
here's the link, if its helpful to anybody: