'Failed to read last sector' when trying to mount DD file

I have a .dd file and want to check what's inside. Many tutorials suggest Disk Image Mounter, but this option doesn't exist.

So I tried the classic way:

mkdir /mnt/image

and

sudo mount -o loop /home/name/Downloads/usb_content.dd

But get this instead

Failed to read last sector (129022): Invalid argument
HINTS: Either the volume is a RAID/LDM but it wasn't setup yet,
   or it was not setup correctly (e.g. by not using mdadm --build ...),
   or a wrong device is tried to be mounted,
   or the partition table is corrupt (partition is smaller than NTFS),
   or the NTFS boot sector is corrupt (NTFS size is not valid).
Failed to mount '/dev/loop42': Invalid argument
The device '/dev/loop42' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?

How can I properly mount dd image?

Edit:

sudo fdisk --list /home/name/Downloads/usb_content.dd

gives:

Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x73736572

Device                                     Boot      Start        End    Sectors   Size Id Type
/home/name/Downloads/usb_content.dd1      1920221984 3736432267 1816210284   866G 72 unknown
/home/name/Downloads/usb_content.dd2      1936028192 3889681299 1953653108 931,6G 6c unknown
/home/name/Downloads/usb_content.dd3               0          0          0     0B  0 Empty
/home/name/Downloads/usb_content.dd4        27722122   27722568        447 223,5K  0 Empty

Partition table entries are not in disk order.

There seems to be four partitions in your image file. If at least one partition has a file system, that Ubuntu can manage, you can try to mount a partition according to the following steps.

• Install kpartx

  sudo apt install kpartx
  

• Use kpartx to map the content of the image file to loop devices

  sudo kpartx -av /home/name/Downloads/usb_content.dd
  

• You should find the mapped loop devices with

  ls /dev/mapper/loop*
  

• Use lsblk to view the mapped content

  lsblk -o name,size,fstype,label,mountpoint /dev/loopN
  

  where N is a number (0 if there were no loop devices before, otherwise the first unoccupied number, for example 7 depending of the number of loop devices that are already mapped). In my case (without any snaps) N = 0 so /dev/loop0.

• Now, lsblk should tell you if there is some file system, and if that is the case, you can create mountpoints and mount [the file systems] with

  sudo mkdir /mnt/lp1  # create mountpoint only once
  sudo mkdir /mnt/lp2  # create mountpoint only once
  ...
  
  sudo mount /dev/mapper/loopNp1 /mnt/lp1
  sudo mount /dev/mapper/loopNp2 /mnt/lp2
  ...
  

  where N is the number that you identified earlier (in my case 0).

• Now you can read the content of the mounted file systems at /mnt/lp1 /mnt/lp2 ...

• Finally, you may want to unmount the file systems and delete the mapping,

  sudo umount /mnt/lp*
  
  sudo kpartx -d /home/name/Downloads/usb_content.dd