Hi Geoffroy. 
I'm little bit confused now.

Two things need to be clear. 

1. SOS kernel image file 
  - What kernel image should I use? with ACRN Hypervisor v0.3
  - org.clearlinux.pk414-sos.4.14.57-69 or org.clearlinux.iot-lts2018-sos.4.19.0-19 ?

2. SOS kernel image location 
  - According to the guide page(https://projectacrn.github.io/latest/tutorials/using_ubuntu_as_sos.html)
The SOS kernel copies to '/boot/acrn/',
sudo cp ~/kernel-build/usr/lib/kernel/org.clearlinux.pk414-sos.4.14.57-69 /boot/acrn/

but in the '/etc/grub.d/40_cutom file says
'linux  /EFI/org.clearlinux/kernel-org.clearlinux.pk414-sos.4.14.57-69'
  - Is this ok? For me, it looks like two different partitions, '/boot/acrn/' is /dev/sda3, and '/EFI/org.clearlinux/' is /dev/sda1.

Thanks
Taekyoung Kim