I found a topic here in the forum that helped me solve this: Ubuntu NFS Server Problem.
It is still true that it is not possible to map a network NFS disk via the Kodi UI, but after applying the modifications as specified in the given topic with the expected NAS network disks available within the HOME folder of the CoreELEC device.
This is probably a actual version of KODI problem and not a CoreELEC or ODROID N2 problem.