JabRef version 5.0, MacOS 10.14.16
I added a citation, and autogenerated a cite key, it contains a non-ASCII letter.
According to a 7-year old issue:
The key generator handles accented and other non-ASCII characters by replacement with ASCII characters deemed equivalent. If you have issues where this is not working properly, we'd be happy to look into it.
https://sourceforge.net/p/jabref/bugs/155/

@InProceedings{bakki2018modèle,
author = {Aïcha Bakki},
date = {2018},
title = {Modèle et outil pour soutenir la scénarisation pédagogique de MOOC connectivistes},
file = {:/Users/stian/Downloads/Thèse_BAKKI_AICHA_Version_F.pdf:PDF},
year = {2018},
}
JabRef version 5.0, MacOS 10.14.16
I added a citation, and autogenerated a cite key, it contains a non-ASCII letter.
According to a 7-year old issue: