Can someone who’s also downloaded v1.1 confirm what @hamsterPL is seeing please?
That would be really helpful to narrow down the issue as I’m not able to reproduce it 
Try this workaround:
- Open the project, choose File -> “New C++ class”, create any dummy class
- Restart the editor.
- Try packaging again.
This workaround has been suggested in the forums for Blueprint-only projects that need to use C++ plugins. Maybe it works for me because I have Visual Studio installed, really not sure.
Another thing - are you packing with build configuration of “Development” or “Shipping”?
Both work for me, although shipping needs a workaround described in this answer hub post (without which it throws a “failed to open descriptor file” error).
Hmm…I’m not using anything substance related in this project at all! That’s really odd.
Did it tell you which assets were problematic? None of the Epic content in the project (eg: the bots) seem to use the Susbtance plugin either. The Substance plugin is free in any case, but still I’m not sure why the project seems to need it.