[Android Software Development] jaaguar:
Hello, i was wondering if modifying some samsung galaxy SM-J320[something] nougat rom, to work on SM-J320FN (it has only android5.1.1 (lollipop) stock rom as far as im aware and i have searched quite a lot).

The thing is, i have the SM-J320FN (twrp and rooted) and for a while i ran various custom roms (based on nougat) on it with no problems. But then about a year ago it bootlooped on resurrection remix (which i had run with not many problems for 1/2 year). Then every custom rom (i tried RR, DotOS, ViperOS and more) began to give me a bootloop, only flashing the stock rom booted.

I wiped and formated everything i could, tried same country stock rom that i had originally and a different country one (thinking maybe the custom roms were not happy with something inside the stock rom that it was flashed after, but logically it does not seem even possible, as before flashing the custom one, the old one is wiped), but custom rom's just did not boot anymore. I could not log the boot either because it had boot animation but nothing showed in adb, i guess it did not get so far that it could connect with adb.

I suspect this may be caused by my camera not working (some hardware part most likely got damaged), because i think wiping my phone completely and flashing stock rom with Odin should restore every software part on the phone thus it would have to be something with hardware that's causing custom roms to bootloop, how else could the problem persist (i obviously might be wrong).

I don't remember when exactly the camera stopped working but i know for a fact that i had a custom rom at the same time, and it did not bootloop (for some time at least) and im also curious why this has not ever stopped the stock rom from booting if it is the case.

So basically i wish i could do two things. Firstly find what makes the stock roms able to boot correctly opposed to the custom ones. And secondly implement this to a higher version rom or a custom rom (Nougat). Come to think of this, it seems a useful step to look how did the people that made these Nougat based rom's for SM-J320FN modify the rom so that it could run on it, the source code is open after all.

Why i want to have a higher android version on my phone? Because my countrys corona close contact detection app supports only 6.0 or higher and my banking app recently notified me that they will soon end support for my android version too (this is the real pusher for me as i use it very frequently and there is not really an alternative). And it would be nice to have some other apps too, that compatible with Lollipop.

And yes, i know, just buying a newer phone would solve all my problems :D But im a very minimalistic (and without money) person. The fact that i own a phone that is still working (or fixable) stops me mentally from buying a new one. Also as one would guess, i like tinkering with this kind of stuff (i study CS currently) and building a rom myself for my phone sounds like a cool and challenging project, as i have not done anything like this before.

Anyways, i kinda got carried away with this post, and maybe it would have been wiser to post this separately in the Samsung J3 (2016) section of xda instead, not as a reply here. But for now im tired and have to sleep so i'll just post this and will come back later to read this over, fix some mistakes (not a native english speaker) and add things i maybe missed.

If anyone read this through, im impressed :) and if you have the knowledge/time to answer then i Thank You in advance!