I remember there was an issue with overlays with older versions of NOOBS, which has been fixed.
You therefore could try to install a current version of NOOBS, or ditectly install LibreELEC.
Hi awiouy indeed the whole problem was that I thought I had an RPI2 and it was an RPI B+.
So, when I tried installing LibreElec I tried to install the WRONG RPI2/3 image.. and Noobs instead would download the correct version, that's why it did work with NOOBS.
The sad part is that your great addon won't work below RPI2, right? So basically it's a no go! I'll have to look for an alternative (it works fine in the RPI3s I have). Thanks!