[Samsung Galaxy J2 ROMs, Kernels, Recoveries, & Oth] Prove N.:
even more digging-ups by enabling emdlogger1 . Well, it boots, then somehow crashes and restart, but it did give me lots of new information

late edit: I forgot some details. Some binaries (ccci_fsd + ccci_mdinit, which, by the name implies, might control the modem) requires emdlogger1, or rather, property init.svc.emdlogger1 to 'running', then 'stopped'. That's why I'm digging this even though Samsung disabled by default for a reason.

part of the log:

09-02 07:53:14.210 452 454 D EMDLOGGER1: not detect SD card is inserted. after 5 seconds
09-02 07:53:14.210 452 454 D EMDLOGGER1: onStartPolling: SD card is ready, record log on SD card
09-02 07:53:14.210 452 454 D EMDLOGGER1: Create log file on SD card
09-02 07:53:14.211 452 454 I EMDLOGGER1: debug property persist.mtklog.mdlog.path value is none
09-02 07:53:14.211 452 454 I EMDLOGGER1: Customize Prop file exist.
09-02 07:53:14.211 452 454 I EMDLOGGER1: Log Save debug.mdlogger.log2sd.path = internal_sd.
09-02 07:53:14.211 452 454 I EMDLOGGER1: Auto Run com.mediatek.log.modem.enabled = false.
09-02 07:53:14.211 452 454 I EMDLOGGER1: Log Recycle size = .2000.
09-02 07:53:14.212 452 454 D EMDLOGGER1: Get auto start mode: 0
09-02 07:53:14.213 452 454 I EMDLOGGER1: debug property persist.mtklog.mdlog.path value is none
09-02 07:53:14.213 969 969 D ConstraintsHelper: construct key=kill_app_longpress_back available=true
09-02 07:53:14.213 452 454 I EMDLOGGER1: Customize Prop file exist.
09-02 07:53:14.213 452 454 I EMDLOGGER1: Log Save debug.mdlogger.log2sd.path = internal_sd.
09-02 07:53:14.213 452 454 I EMDLOGGER1: Auto Run com.mediatek.log.modem.enabled = false.
09-02 07:53:14.213 452 454 I EMDLOGGER1: Log Recycle size = .2000.
09-02 07:53:14.213 452 454 D EMDLOGGER1: Get auto start mode: 0
09-02 07:53:14.215 452 454 D EMDLOGGER1: Success to create log folder /sdcard/log/MDLog1_2019_0902_075314
09-02 07:53:14.215 452 454 D EMDLOGGER1: Generate log folder tree file, isFolderTrue:1, isNewCreat:0
09-02 07:53:14.215 452 454 E EMDLOGGER1: Failed to open/create tree file /mnt/sdcard/log/cp/mdlog1/file_tree.txt, errno=2
09-02 07:53:14.215 452 454 D EMDLOGGER1: Generate version file
09-02 07:53:14.217 452 454 D EMDLOGGER1: File /sdcard/log/MDLog1_2019_0902_075314/version_info.txt open.
09-02 07:53:14.217 452 454 D EMDLOGGER1: MAL_GetModemVersion: 1
09-02 07:53:14.218 452 454 D EMDLOGGER1: Modem Version: MOLY.LR9.W1444.MD.LWTG.TC10.SP.W17.02.LTE.P2.P1 2018/04/02 13:25
09-02 07:53:14.218 452 454 D EMDLOGGER1: Android Version: alps-mp-m1.mp8.tc10sp
09-02 07:53:14.218 452 454 D EMDLOGGER1: getGsmProjectBaseband: MD idx is 1
09-02 07:53:14.218 452 454 D EMDLOGGER1: Project Version: unknown
09-02 07:53:14.219 452 454 D EMDLOGGER1: Success to write version file.

09-02 07:53:23.591 452 454 I EMDLOGGER1: MDLCTL_END_MEMORY_DUMP: channel clear, dump ended
09-02 07:53:23.591 452 454 D EMDLOGGER1: Stop Buffer: stop 0!
09-02 07:53:23.591 452 454 D EMDLOGGER1: Close log file and delete the pointer.
09-02 07:53:23.591 452 454 D EMDLOGGER1: Clean Close file /sdcard/log/cpcrash_MDLog1_2019_0902_075319.bin..bin.
09-02 07:53:23.591 452 454 D EMDLOGGER1: Close log file: Success.
09-02 07:53:23.591 452 454 D EMDLOGGER1: File's new name is: /sdcard/log/cpcrash_MDLog1_2019_0902_075319.bin
09-02 07:53:23.592 452 454 D EMDLOGGER1: PlsLogWriter: Stop polling, type:1
09-02 07:53:23.592 452 454 D EMDLOGGER1: Polling memory dump: Polling is done! EE
09-02 07:53:23.592 452 454 D EMDLOGGER1: enter titan upload mode in engine

full logcat+ partial last_kmsg + logs captured by emdlogger1 itself are attached here because I think i'm missing something.