The tricky part it’s that you can have a valid file listing but corrupted file if disk order is not good.

I had to try all the disks permutation order anc check if the pdf file was corrupted or not; this is the good order:

losetup --find --show disk1.img
losetup --find --show disk2.img
mdadm --create --assume-clean --level=5 --raid-devices=3 /dev/md0 /dev/loop1 missing /dev/loop0
mount /dev/md0 /mnt/raid
ls -lah /mnt/raid
total 4,1M
drwxrwxrwx 2 root root 1,0K 8 avril 08:12 .
drwxr-xr-x 1 root root 22 15 mai 22:14 ..
-rwxrwxrwx 1 sky lpadmin 4,1M 7 avril 18:44 imw_1337.pdf
The flag is in the pdf file

Original writeup (https://skyfr.notion.site/Intergalactic-Recovery-45097c189f684e2580b7e344bc7498a3).