Comment 4 for bug 1992358

Looking at the old /usr/lib/systemd/scripts/nfs-utils_env.sh[1] script, it looks like another variable was reserved for NFSD command-line arguments (RPCNFSDOPTS):

(...) (line 12)
echo RPCNFSDARGS=\"$RPCNFSDOPTS ${RPCNFSDCOUNT:-8}\"
                    ^^^^^^^^^^^

And RPCNFSDOPTS is handled by the conversion script[2], and the "-V" option is valid for it:
# options for nfsd found in RPCNFSDOPTS
OPTS_NFSD = 'dH:p:rR:N:V:stTuUG:L:'

So to amend my previous comment, you should remove "-V 2" from RPCNFSDCOUNT in /etc/default/nfs-kernel-server and move it to a new entry:

RPCNFSDOPTS="-V 2"

And then upgrade nfs-kernel-server/nfs-common again and the conversion script should finish the job. This will correctly translate the "-V 2 8" you had before to:

[nfsd]
vers2 = y
threads = 8

1. https://git.launchpad.net/ubuntu/+source/nfs-utils/tree/debian/nfs-utils_env.sh?h=applied/ubuntu/focal-devel#n12
2. https://git.launchpad.net/ubuntu/+source/nfs-utils/tree/debian/nfsconvert.py?h=applied/ubuntu/jammy-devel#n15