The command wipefs can be used to examine the read partition boot-signatures, and possible 'kill' them.
# wipefs /dev/sda DEVICE OFFSET TYPE UUID LABEL sda 0x36 vfat D14A-DCD7 sda 0x0 vfat D14A-DCD7 sda 0x1fe vfat D14A-DCD7 sda 0x8001 iso9660 2020-02-25-20-44-34-00 ISOIMAGE sda 0xe6e907e00 gpt # dd if=/dev/zero of=/dev/sda bs=512 count=1 1+0 records in 1+0 records out 512 bytes copied, 0.00808424 s, 63.3 kB/s # wipefs /dev/sda DEVICE OFFSET TYPE UUID LABEL sda 0x8001 iso9660 2020-02-25-20-44-34-00 ISOIMAGE sda 0xe6e907e00 gpt # wipefs -a /dev/sda /dev/sda: 5 bytes were erased at offset 0x00008001 (iso9660): 43 44 30 30 31 /dev/sda: 8 bytes were erased at offset 0xe6e907e00 (gpt): 45 46 49 20 50 41 52 54 /dev/sda: calling ioctl to re-read partition table: Success # wipefs /dev/sda