Hi. I saw this bug (https://github.com/xpawelsky/RipImport/issues/1) and this is also affecting me importing .pkg files. It works on Windows, but I always get some form of the above message on Linux. I've tried fixes like what you mentioned there (forcing little-endian with the < symbol) and changing the number of file.read bytes but I so far haven't gotten a successful import. I seem to get (some of) the data because I get object names but no actual mesh.
This was tested on both Windows and Linux with Blender 2.83.
Thanks.