NFS export of mounted disk issues

[willat8]

Version (k3OS / kernel)

k3os v0.22.2-k3s2r0
kernel 5.10.63-v8+

Architecture
aarch64

Describe the bug
I have mounted a USB disk at /media/usb and configured my /etc/exports like /media/usb *(ro,all_squash,insecure). NFS service is started by

sudo mkdir -p /var/lib/nfs/sm
sudo service nfs start

When trying to mount this share on any client, mount tries nfsv4.2 and hangs forever. Manually specifying nfsvers=3 when mounting works. Also exporting any other part of the filesystem on k3os works fine and mounting on the client doesn't hang.

Expected behavior
Mounting the share using nfsv4.2 should work, or at least not hang forever and fallback to earlier NFS versions.

Additional context
This worked fine on k3os v0.21.x and earlier.