How to fix mount errors when trying to mount the raw image that converted from android sparse image?
The file system might not be in the beginning of the raw partition image.
First you need to convert the image from sparse to raw, using either simg2img or sparse_img_to_ext4.py.
Then, you need to find the beginning of the actual partition, binwalk is my favorite tool for that:
$ binwalk super.raw.img

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
1048576       0x100000        Linux EXT filesystem, rev 3.0, ext2 filesystem data, UUID=8f83745e-c212-5aab-a776-4aeed9fad9fa, volume name &quot;/&quot;
[...many many irrlevant hits...]

Now you can mount the file system using the first offset from the binwalk output:
sudo mount super.raw.img -t ext4 -o ro,loop,offset=0x100000 /media/super/