So LXD only activates the logical volumes when it needs to mount the volume, this is so we don’t keep unnecessary devices active in the system.
You can manually activate using:
sudo lvchange --activate y --ignoreactivationskip /dev/storage2-vg/custom_default_recovery
And then when you’re done, after unmounting, do
sudo lvchange --activate n --ignoreactivationskip /dev/storage2-vg/custom_default_recovery