For comparison, on my Debian Bookworm (aka "testing" but in hard freeze and full freeze in a few days I think, stable release in june) here...

    ...$  lsmod|grep nf_table    (tried without any just to make sure) 
    ...$  unshare -U -m -n -r
    unshare: unshare: failed: Operation not permitted
    ...$  /sbin/nft add table inet filter
    Error: Could not process rule: Operation not permitted
    add table inet filter
    ^^^^^^^^^^^^^^^^^^^^^^

    root #  cat /proc/sys/kernel/unprivileged_userns_clone
    0