OpenMediaVault NFS exports cannot be mounted - Permission denied: Perhaps this host is disallowed or a privileged port is needed
OMV has an /export virtual root set a secure (while the subfolders are insecure). It tells in comments NFSv4 related this kill gvfs nfs backend which in https://gitlab.gnome.org/GNOME/gvfs/blob/master/daemon/gvfsbackendnfs.c#L202 search the shorted match (always this virtual root thus)
I am quite lacking standard wise, I patch around the issue by a fallback (replace export by the initila mount_spec->mount_prefix if EACESS and retry). Requires mangling the code around a bit. Dirty.
But it might be best to remove this mount point shortening instead.
I do not see the point of the while shortinging (except not mounting twice the same export with different subfolder levels, but is this an issue ?)