disk pressure on Ubuntu nodes because missing mount points

In my dev environment I have both OpenSuse-hardened and Ubuntu-plain nodes.

I've noticed the Ubuntu nodes frequently being under disk pressure.

This is due to not having a lot of space in /var:

df -h |grep ^/ |grep -v dev/sd
/dev/mapper/vg-lv_root    4.6G  1.8G  2.5G  43% /
/dev/mapper/vg-lv_home    4.0G   52K  3.8G   1% /home
/dev/mapper/vg-lv_opt     1.8G  1.3G  413M  77% /opt
>> /dev/mapper/vg-lv_var  4.9G  3.8G  891M  81% /var  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
/dev/mapper/vg-lv_tmp     2.0G   32K  1.9G   1% /tmp
/dev/mapper/vg-lv_varlog  4.9G   24M  4.7G   1% /var/log
/dev/mapper/vg-lv_vartmp  919M   32K  856M   1% /var/tmp

The problem/inconsistency is that the overall disk is large, but it has most space on pre-existing volumes which are not mounted:

# lsblk -T -o NAME,SIZE
NAME                   SIZE
sda                    100G
├─sda1                   4M
├─sda2                 250M
└─sda3                99.8G
  ├─vg-lv_root         4.7G
  ├─vg-lv_tmp            2G
  ├─vg-lv_var            5G
  ├─vg-lv_vartmp         2G
  ├─vg-lv_varlog         5G
  ├─vg-lv_varlogaudit    2G
    ^^ not used
  ├─vg-lv_home           4G
  ├─vg-lv_etcd          10G
    ^^ not used
  ├─vg-lv_containerd  29.9G
    ^^ not used
  ├─vg-lv_kubelet     29.9G   
    ^^ not used
  └─vg-lv_opt          1.9G
    ^^ not used

Comparatively, OpenSuse nodes are fine, because other volumes (larger ones) are mounted in some /var sub-directories:

# df -h |grep ^/ | grep -v dev/sd
/dev/mapper/vg-lv_root         4.6G  1.6G  2.7G  38% /
/dev/mapper/vg-lv_home         4.0G   64K  3.8G   1% /home
/dev/mapper/vg-lv_opt          1.8G  1.3G  413M  77% /opt
/dev/mapper/vg-lv_tmp          2.0G   40K  1.9G   1% /tmp
/dev/mapper/vg-lv_var          4.9G  1.4G  3.3G  30% /var
>> /dev/mapper/vg-lv_kubelet       30G   73M   29G   1% /var/lib/kubelet
>> /dev/mapper/vg-lv_containerd    30G   14G   15G  49% /var/lib/rancher/rke2/agent/containerd
>> /dev/mapper/vg-lv_etcd         9.9G   24K  9.4G   1% /var/lib/rancher/rke2/server/db
/dev/mapper/vg-lv_varlog       4.9G   53M  4.7G   2% /var/log
/dev/mapper/vg-lv_vartmp       2.0G   40K  1.9G   1% /var/tmp
>> /dev/mapper/vg-lv_varlogaudit  2.0G  400K  1.9G   1% /var/log/audit