as I’m on my way to make KiCad 4 and 5 working in parallel, I tried to modify the path to the default project template file kicad.pro
By default, this is the file /usr/share/kicad/template/kicad.pro
with the default environment variable KICAD_PTEMPLATES=/usr/share/kicad/template/
Now I tried to set the KICAD_PTEMPLATES to a different path, which contains a kicad.pro file, which is explicitly for KiCad 4. But it seems, that the variable only defines, where template projects can be found. KiCad 4 allways looks in that fixed path (/usr/share/kicad/template/kicad.pro) for the default project template, which is not, what I expected.
With KiCad 5, the situation is the same. As stated in the KiCad blog, the default kicad.pro file must not contain any libraries, when used for KiCad 5: https://kicad.org/post/symbol-lib-table/ (paragraph 3)
We have here another conflict between the versions 4 and 5.
I’ll report a bug…