How to capture all disks that don’t have a file system

lsblk -o NAME,FSTYPE -dsn

This will print a list of block devices that are not themselves holders for partitions (they do not have a partition table). The detected file system type is in the second column. If its blank there is no recognized file system.

So to get the output you want in one command

lsblk -o NAME,FSTYPE -dsn | awk '$2 == "" {print $1}'