Identify the total sum of the LVM Volume Group
vgdisplay -C -o vg_size --units g --noheading --nosuffix
Identify the total sum of all LVM thin volumes (VM disks), ignoring the root/swap/data.
lvs -o lv_size --units g --noheading --nosuffix | tail +4 | awk '{sum += $1} END {print sum}'
Subtract the LVM thin volume size from the LVM Volume Group size to identify free space available (or overprovisioned).