NFS root mounts are handled by nfsmount which is part of the klibc-utils package. nfsmount only accepts integers for the 'vers' argument. And only values 2 and 3 are valid:
$ ./usr/bin/nfsmount -o vers=4.1
4.1: invalid value for vers
$ ./usr/bin/nfsmount -o vers=4
./usr/bin/nfsmount: bad NFS version '4'
$ ./usr/bin/nfsmount -o vers=3
./usr/bin/nfsmount: need a path
The kernel does support NFSv4:
./lib/modules/5.13.0-1011-raspi/kernel/fs/nfs/nfsv4.ko
NFS root mounts are handled by nfsmount which is part of the klibc-utils package. nfsmount only accepts integers for the 'vers' argument. And only values 2 and 3 are valid:
$ ./usr/bin/nfsmount -o vers=4.1
4.1: invalid value for vers
$ ./usr/bin/nfsmount -o vers=4
./usr/bin/nfsmount: bad NFS version '4'
$ ./usr/bin/nfsmount -o vers=3
./usr/bin/nfsmount: need a path
The kernel does support NFSv4: 5.13.0- 1011-raspi/ kernel/ fs/nfs/ nfsv4.ko
./lib/modules/