The file at this link: http://downloads.sierrawireless.com/AirPrime/WP77xx/Release11/Legato-Dist-Source-mdm9x06-SWI9X06Y_02.22.12.00.tar.bz2 is corrupt and unusable.
Is it same problem as this one?
I think the symptom might be the same but I have tried to extract it both on Windows using 7zip and on Linux, OpenSUSE Leap 15 and they both show corrupted data.
Maybe you can try ubuntu 14.
I can try but that is still not a good solution. The real solution is that Sierra should upload a bzip file that can be used by a recent OS using recent software.
Here says you can try lbunzip2.
That unfortunately also fails, but with “bad block header magic” instead.
Using Ubuntu 14.04 works, but this is a seriously old distribution, so I still consider the files to be broken unfortunately.
Probably related to the version of zip tool