How can I see my NFS share in any file manager on Android 6.0.1?
Turns out an option in SuperSU blocked me from seeing the content of my mounts. I needed to disable the "Mount namespace separation" option in SuperSU app. Only then the mounts will be visible to other apps! Disabling namespace separation may cause security flaws, but I don't see any other solution yet. Reboot the device, mount your shares and everything will be as expected.

Found the solution here: https://stackoverflow.com/a/33611664