I was still having trouble with blender imports even after I updated to 5.6.0b3 … until I switched to the official ubuntu blender build from apt, which unfortunately is only at version 2.76b.
By only downloading and extracting the latest stable tarball from blender.org, you essentially leave blender uninstalled. It just runs as a standalone app from a single directory (in my case /opt/blender-2.78a/)
I’m left guessing that Unity is looking for blender somewhere in usr/lib or usr/share - two directories not touched through a standalone blender “installation.”
I solved my blender import problem by switching my blender source to this PPA:
It properly installs the latest stable master (or bleeding edge commit). I’ve now got 2.78a configured properly, and blender imports are working flawlessly.
I originally downloaded and extracted blender to my /opt/blender** directory, added that to my PATH from .bashrc:
PATH = $PATH:/opt/blender-2.78a
export PATH
I could then run blender in any directory from terminal with just “blender” but was getting this error in my Editor.log after trying to import a new .blend asset:
Error: execv(blender) no such file or directory.
[…/Editor/Src/AssetPipeline/FBXImporter.cpp line 359]
exporting PATH like that will only make the change for the current terminal session. If you want this change permanent, and across all environments, you would need to edit the PATH variable in your ~/.profile or /etc/profile, and logout/login so the display manager picks up the path definition and makes it default for all applications.
You can also use ~/.bashrc but note the DE may not pick this up and it will only apply to commands launched via the terminal.
You could also just modify the unity launcher script to include the modified PATH, or you could symlink /usr/bin/blender to your preferred blender executable