Not me. Ubuntu is my daily driver.
Sorry for my misinterpretation. CDEX, although opensource, seems to be a windows app.
Not really. Kodi (and LibreELEC) is designed to be a application CLIENT. It is not meant to be a server. It does have SMB because Windows supports it basically as its only sharin, Linux can do both SMB and NFS quite easily. NFS server is not implement in LE because it would add to LibreELEC becoming bloated.
I don't have a problem with this, I just think it's easier to mount a directory structure from a nfs-server on linux then from a SMB server. My LE box has it own hdd, so I have to put files on it on regular base. And yes it would be easier to put everything on my PC or a NAS and serve it to LE. But I'm kind of a low electricity consumer nerd and don't want to run a extra device just to watch a movie.
Probably nfs would indeed just taking space on 90% of the LE-devices.