[Samsung Galaxy J4+ Guides, News, & Discussion] rudi021:
1. please read this very carefuly.this guide is made from my personal experience. :o

like some members of this forums told me and i think a little about it,there can be problem about downgrade to oreo with devices who have unlock device from operator.but i believe can be easily unlock with talk with operators,not sure,but be best to check it out by self.

firstly i am not noob,i am developer and compiler for many mtk device. sadly this is my FIRST

samsung device also snapdragon. so for me completely unknown.i want in first root and do custom roms but untill now

i dont find any device tree for this device.kernel source i have but device and vendor tree not.then i found i can

flash gsi on this device. so i do as i will explain in following text.

2. as many other of you i have update device on PIE and next days i install update i found possibility to flash gsi,

so i try. i found patched pie boot.img and try to flash gsi roms but none of them isnt boot.so i stop and again read gsi guide

for flash gsi.i read that devices shipped with some firmwares have chance to flash gsi roms.so i found oreo rom

for our device and flash it with odin.rom is boot without any problems.i set up all things as normall(google account)

and after all setup i go to device info and tap on build numbers 7-10 times and then developer settings is open,then i

checked if is there oem unlocking.(if you dont set up google account this settings will not shown(oem unlocking)).

when i see is ok and there,i power off device,go to download mode and connect with pc,and open odin,

and flash twrp(again thanks to ashyx).dont let odin to boot system(turn off auto rebbot in option),

so i reboot to recovery,go to wipe,choose format data,write yes and swipe.

after that i reboot to recovery you MUST flash oreo enforcing.zip,rmm and oreo patched boot.and go to install choose micro sd card and go to flash img. choose gsi rom you want and

flash it as system(pop up windows will ask wich partition you choose(system),then swipe to flash,after flashing you flash magisk,

and go to mount and mount system and reboot to system. firstly your device can reboot once-twice during,but dont worry

after that will go to boot and in short time,one- two minutes will boot.

3.now i must warning you.many of gsi roms work properly,but have many bugs.mtp dont works with pc in boot up,but in recovery

works without problems.for me is not problem,i can live with it.

3.1.sim card 2 is work but sim card 1 is not see it.also i can live with it.most of time i use 1 sim card,not both.

3.2.fm radio isnt show,and not work.

4.in short i give you again flash guide.

go to recovery (must be in oreo)

go to wipe-format data,write yes and swipe to format (many say to need back to recovery,i didnt do that but is your choice).

go to sd card and install oreo enforcing.zip,RMM bypass.zip and oreo patched boot.img

go to install and choose flash.img and choose gsi you want,and flash as system

go to install zip and flash magisk

then go to mount,mount system and reboot to system

device will reboot twice or more time and then after minute or two will reboot.be calm.

after device is reboot,enjoy.:cool::good:

i will post some screenshots of booted gsi roms.oreo and pie.

list of booted gsi rom so far:

1. aex 5.7 oreo

2. aex 6.5 pie

3. aosdp pie(this rom not show network and sim cards)

4. aosp by phusson pie

5. bootlegger oreo

6. descendant 3.0 pie

7. dot os pie(dont show network and simcards)

8. havoc os pie

9. lineage 16 pie

10. RR oreo

11. RR pie

12. system DU oreo

13. xenon hd oreo

GSI with errors:

AOSDP (not shown sim cards,no network,all other stuff work,off course no fm radio)

Evolution X (dont want to boot.)

Octopus OS (dont boot)

Viper OS Official (not shown sim cards,all other stuff work except fm radio)

Dot OS (dont show sim cards,no network,no fm radio)

Liquid Remix (dont boot)

Omni rom (boot but goes constantly on reboot)

Pixel Expirience (boot but no sim cards and no network and no fm radio)

people one more notice: j4+ is ARM A ONLY device,dont flash any other gsi.