macOS X Catalina cannot be installed on Macintosh HD

I am currently on a Early 2015 Macbook Pro on El Capitan 10.11.6.

I am looking to update to Catalina but I get the error message in the title of this post. I got this error after doing diskutil verify disk. Before that I got the message that I am missing a firmware partition.

my diskutil list information is as follows:

/dev/disk0 (external, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *960.0 GB   disk0
1:                        EFI EFI                     209.7 MB   disk0s1
2:                  Apple_HFS Macintosh HD            959.2 GB   disk0s2
3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
/dev/disk1 (disk image):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        +8.4 GB     disk1
1:                        EFI EFI                     209.7 MB   disk1s1
2:                  Apple_HFS InstallESD              8.1 GB     disk1s2

Update: Upgraded to Sierra. Cannot advance to High Sierra or Catalina due to the same missing firmware partition error.

Update 2: System Information says this:

Macintosh HD
Available:  920,7 GB (920.699.588.608 bytes)
  Capacity: 959,18 GB (959.180.382.208 bytes)
  Mount Point:  /
  File System:  Journaled HFS+
  Writable: Yes
  Ignore Ownership: No
  BSD Name: disk0s2
  Volume UUID:  FA831049-5446-3393-952B-D5EC501F181C
  Physical Drive:
  Device Name:  OWC Aura SSD
  Media Name:   OWC Aura SSD Media
  Medium Type:  Rotational
  Protocol: PCI
  Internal: No
  Partition Map Type:   GPT (GUID Partition Table)

The problem is that you have a third-party internal SSD. You need an OWC firmware update in order to upgrade past High Sierra.

Installing High Sierra on OWC Aura SSD - missing firmware partition

You should probably upgrade to High Sierra first, then upgrade to Catalina. Installing High Sierra will upgrade the firmware. Also, High Sierra can boot from both JHFS+ and APFS partitions. Catalina can only boot from APFS which requires the Mac to have the firmware update. If you have a SSD, then the upgrade to High Sierra should also convert the boot partition to APFS. Otherwise, HDD will be converted after installing High Sierra.