Comment 2 for bug 1983620

The NFS server is quite capable of running NFSv4 as can be seen from the following:

Filesystem Type Size Used Avail Use% Mounted on
tmpfs tmpfs 185M 3.2M 182M 2% /run
192.168.8.20:/volume3/nfs/RPi4/Ubuntu/jammy/root nfs 60G 3.9G 53G 7% /
tmpfs tmpfs 923M 0 923M 0% /dev/shm
tmpfs tmpfs 5.0M 0 5.0M 0% /run/lock
none tmpfs 923M 0 923M 0% /tmp
none tmpfs 923M 0 923M 0% /var/tmp
192.168.8.20:/RPi4/Ubuntu/jammy/boot nfs4 253M 149M 104M 59% /boot/firmware
tmpfs tmpfs 185M 4.0K 185M 1% /run/user/1000

This is the state after a network boot with NFSv3. Note that

  192.168.8.20:/volume3/nfs/RPi4 and
  192.168.8.20:/RPi4

are identical: the first is served with NFSv3, the second with NFSv4.