Solution:
Apparently it's located in ./node_modules/electron/dist
in this directory you will find the electron binary and libnode.so
Additional information:
If you try to use setcap
to add permissions for electron on ./node_modules/electron/dist/electron
it will complain about missing the shared lib libnode.so
even though its there. This is a intended by linux and you have to link it manually, also see this question about it.