NFS mounts do not work and you receive the error message: 

mount: bad option; for several filesystems (e.g. nfs, cifs) you might need a /sbin/mount.<type> helper program.

Example of this Problem

root@len:/home/kevin# mount -v -t nfs -o proto=tcp,vers=4,nolock geminivpn:/home/kevin/DATA /media/kevin/DATA
mount: /media/kevin/DATA: bad option; for several filesystems (e.g. nfs, cifs) you might need a /sbin/mount.<type> helper program.
Filesystem Size Used Avail Use% Mounted on
udev 3.8G 0 3.8G 0% /dev
tmpfs 783M 1.6M 781M 1% /run
/dev/sda12 156G 69G 79G 47% /
tmpfs 3.9G 120M 3.8G 4% /dev/shm
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/sda10 512M 4.0K 512M 1% /boot/efi
tmpfs 783M 60K 783M 1% /run/user/1000
/dev/sda11 4.0G 1.8G 2.2G 45% /media/kevin/LENOVO
/dev/mapper/DATAVOLUMELUKS 12G 7.4G 3.8G 67% /media/kevin/DATAVOLUMELUKS
root@asusvpn:/home/kevin/LOCAL 395G 313G 63G 84% /mnt

Cause of the Problem and Solution

This problem occurs because the system requires the systemd service nfs-common to be installed and running as a service.

The solution is to install nfs-common and start the service

root@len:/home/kevin# apt install nfs-common
Reading package lists… Done
Building dependency tree
Reading state information… Done

Preparing to unpack …/5-nfs-common_1%3a1.3.4-2.5ubuntu3.4_amd64.deb …
Unpacking nfs-common (1:1.3.4-2.5ubuntu3.4) …
Setting up libtirpc-common (1.2.5-1) …
Setting up keyutils (1.6-6ubuntu1) …
Setting up libnfsidmap2:amd64 (0.25-5.1ubuntu1) …
Setting up libtirpc3:amd64 (1.2.5-1) …
Setting up rpcbind (1.2.5-8) …
Created symlink /etc/systemd/system/multi-user.target.wants/rpcbind.service → /lib/systemd/system/rpcbind.service.
Created symlink /etc/systemd/system/sockets.target.wants/rpcbind.socket → /lib/systemd/system/rpcbind.socket.
Setting up nfs-common (1:1.3.4-2.5ubuntu3.4) …
.. .. .. ..
.. .. .. ..
Creating config file /etc/idmapd.conf with new version
Adding system user `statd’ (UID 125) …
Adding new user `statd’ (UID 125) with group `nogroup’ …
Not creating home directory `/var/lib/nfs’.
Created symlink /etc/systemd/system/multi-user.target.wants/nfs-client.target → /lib/systemd/system/nfs-client.target.
Created symlink /etc/systemd/system/remote-fs.target.wants/nfs-client.target → /lib/systemd/system/nfs-client.target.
nfs-utils.service is a disabled or a static unit, not starting it.
Processing triggers for systemd (245.4-4ubuntu3.16) …
Processing triggers for man-db (2.9.1-1) …
Processing triggers for libc-bin (2.31-0ubuntu9.7) …
root@len:/home/kevin# mountnfsgemini

The nfs mounts then work ok