https://community.e.foundation/t/unofficial-build-samsung-galaxy-j3-2016-j3xnlte-e-0-21-n/
there are different versions of the J3 (2016), but for the sc9830a line I created a (really old by now) Nougat build for from the referenced XDA thread. Check your SoC before using… needs to be a Spreadtrum… the American ones are the incompatible ones with this build.
Some Apps are pretty outdated by now, will improve on it in the coming weeks.