Having an Ubuntu 16.04 on a MacBook Pro which won't start any more, I've found out that the superblock entries of my disk seem to be corrupted. So I want to find out the superblock (while running Ubuntu from live USB):

$ dumpe2fs /dev/sda

(as in this question) sais Bad magic number in super-block while trying to open /dev/sda - Couldn't find valid filesystem superblock.

$ sudo mkfs.ext4 -n /dev/sda

(as in the according answer) gives

Creating filesystem with 125026902 4k blocks and 31260672 inodes
Superblock backups stored on blocks:
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
    2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 
    78675968, 102400000

Same output for sudo mke2fs -n /dev/sda as suggested here.

When trying to set a superblock by

$ sudo e2fsck -b BLOCKNUMBER /dev/sda

... the result is always like following, no matter which BLOCKNUMBER is used:

e2fsck: Bad magic number in super-block while trying to open /dev/sda
The superblock could not be read or does not describe a valid ext2/ext3/ext4 filesystem.

So I've skipped trying to reboot with all of the listed BLOCKNUMBERs. (I've just tried the first two of them.)

So, does anyone know what might help in this case? If someone needs further details: I've also created a boot-repair report to pastebin: http://paste.ubuntu.com/p/78vT3HFwyC/ I'm thankful for every hint.


ADDITIONAL INFORMATION (2018 dec 08) :

$ sudo dmesg | grep sda
[    7.008142] sd 0:0:0:0: [sda] 1000215216 512-byte logical blocks: (512 GB/477 GiB)
[    7.008166] sd 0:0:0:0: [sda] Write Protect is off
[    7.008168] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[    7.008311] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[    7.056103]  sda:
[    7.056752] sd 0:0:0:0: [sda] Attached SCSI disk
[  564.880429]  sda:

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