simg2img silenting failing to convert Fairphone 4 super.img?

I want to mount super.img from [Fairphone 4's factory images](https://support.fairphone.com/hc/en-us/articles/18896094650513) .

> file super.img      

super.img: Android sparse image, version: 1.0, Total of 1572864 4096-byte output blocks in 229 input chunks.

I installed the [android-simg2img package](https://aur.archlinux.org/packages/android-simg2img) to convert this to an ext4 image. After executing simg2img, no errors are generated, but trying to mount the file fails.

> file super.raw.img
super.raw.img: data
> sudo mount -o loop ./super.out.img /mnt/image
mount: /mnt/image: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.
       dmesg(1) may have more information after failed mount system call.
> sudo dmesg

[1074956.090619] loop0: detected capacity change from 0 to 12582912
[1074956.092396] FAT-fs (loop0): bogus number of reserved sectors
[1074956.092398] FAT-fs (loop0): Can't find a valid FAT filesystem
[1074956.092450] EXT4-fs (loop0): VFS: Can't find ext4 filesystem
[1074956.092560] EXT4-fs (loop0): VFS: Can't find ext4 filesystem
[1074956.092632] EXT4-fs (loop0): VFS: Can't find ext4 filesystem
[1074956.093484] NILFS (loop0): couldn't find nilfs on the device

How can I mount the image?