NFS server install gives: "/mnt does not support NFS export"

I am trying to install nfs server to my router TP-Link C7 v5 running on this sysupgrade bin

https://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/openwrt-19.07.8-ath79-generic-tplink_archer-c7-v5-squashfs-sysupgrade.bin

per this User Guide

https://openwrt.org/docs/guide-user/services/nas/nfs_configuration

and not meeting with success.

First of all, I believe there is a typo in this line of the User Guide:

opkg update opkg install nfs-kernel-serverSystem

which (probably) should have read:

opkg update opkg install nfs-kernel-server

The amended line however gave shell output that ended in "exportfs: /mnt does not support NFS export."

Shell output:

root@OpenWrt:~# opkg install nfs-kernel-server
Installing nfs-kernel-server (2.3.4-3) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/nfs-kernel-server_2.3.4-3_mips_24kc.ipk
Installing libwrap (7.6-2) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/libwrap_7.6-2_mips_24kc.ipk
Installing libtirpc (1.2.6-2) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/libtirpc_1.2.6-2_mips_24kc.ipk
Installing kmod-fs-nfs-common (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-nfs-common_4.14.241-1_mips_24kc.ipk
Installing kmod-fs-exportfs (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-exportfs_4.14.241-1_mips_24kc.ipk
Installing kmod-crypto-cbc (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-crypto-cbc_4.14.241-1_mips_24kc.ipk
Installing kmod-crypto-cts (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-crypto-cts_4.14.241-1_mips_24kc.ipk
Installing kmod-crypto-sha1 (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-crypto-sha1_4.14.241-1_mips_24kc.ipk
Installing kmod-fs-nfs-common-rpcsec (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-nfs-common-rpcsec_4.14.241-1_mips_24kc.ipk
Installing kmod-fs-nfsd (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-nfsd_4.14.241-1_mips_24kc.ipk
Installing kmod-dnsresolver (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-dnsresolver_4.14.241-1_mips_24kc.ipk
Installing kmod-fs-nfs (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-nfs_4.14.241-1_mips_24kc.ipk
Installing kmod-fs-nfs-v4 (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-fs-nfs-v4_4.14.241-1_mips_24kc.ipk
Installing rpcbind (1.2.5-4) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/rpcbind_1.2.5-4_mips_24kc.ipk
Installing libkeyutils1 (1.6-3) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/libkeyutils1_1.6-3_mips_24kc.ipk
Installing kmod-dax (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-dax_4.14.241-1_mips_24kc.ipk
Installing kmod-dm (4.14.241-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/targets/ath79/generic/kmods/4.14.241-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d/kmod-dm_4.14.241-1_mips_24kc.ipk
Installing libdevmapper (2.03.02-2) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/libdevmapper_2.03.02-2_mips_24kc.ipk
Installing nfs-utils-libs (2.3.4-3) to root...
Downloading http://downloads.openwrt.org/releases/19.07.8/packages/mips_24kc/packages/nfs-utils-libs_2.3.4-3_mips_24kc.ipk
Configuring kmod-crypto-cts.
Configuring kmod-fs-nfs-common.
Configuring kmod-fs-exportfs.
Configuring kmod-crypto-cbc.
Configuring kmod-crypto-sha1.
Configuring kmod-fs-nfs-common-rpcsec.
Configuring kmod-fs-nfsd.
Configuring kmod-dax.
Configuring kmod-dm.
Configuring libwrap.
Configuring libkeyutils1.
Configuring kmod-dnsresolver.
Configuring kmod-fs-nfs.
Configuring kmod-fs-nfs-v4.
Configuring libtirpc.
Configuring rpcbind.
Configuring libdevmapper.
Configuring nfs-utils-libs.
Configuring nfs-kernel-server.
exportfs: /etc/exports [1]: Neither 'subtree_check' or 'no_subtree_check' specified for export "*:/mnt".
  Assuming default behaviour ('no_subtree_check').
  NOTE: this default has changed since nfs-utils version 1.0.x

exportfs: /mnt does not support NFS export

I tried amending the reference to the share location in /etc/exports so it is no longer /mnt but /mnt/dump2.

Shell output:

root@OpenWrt:/mnt# mkdir dump2
root@OpenWrt:/mnt# vi /etc/exports
root@OpenWrt:/mnt# service nfsd reload
exportfs: /etc/exports [1]: Neither 'subtree_check' or 'no_subtree_check' specified for export "*:/mnt/dump2".
  Assuming default behaviour ('no_subtree_check').
  NOTE: this default has changed since nfs-utils version 1.0.x

exportfs: /mnt/dump2 does not support NFS export
root@OpenWrt:/mnt# 

What could have gone wrong? What should I try next?

If anything might interfere with nfs, ksmbd server is running on this rounter. OtherwiseI have installed a whole bunch of packages but did not do much configuration.

Why nfs (esp. when I have ksmbd)? I am just seeing how different things work.