Most of the Samsung Galaxy J5s of yesteryear run Android 7.0 (Nougat). However, new reports indicate that some of these phones are receiving an update. This software skips 8.0 Oreo and goes straight to 8.1 instead. So far, reports indicate that 2017 J5s in Poland and India have seen this version of the Samsung Experience ROM.
https://www.notebookcheck.net/Update-to-Android-8-1-available-for-Samsung-Galaxy-J5-2017-in-some-countries.325642.0.html