Thanks for your help !
I followed the procedure in the Linux guide, but the image was too big and I wanted to start from scratch with only linux-fscl.
I will give a try with meta-imx so, did you use the guide procedure and then dd the .wic into the eMMC ?
Interestingly, I tried buildroot and the kernel 6.6 creates the same issues with linux-imx as source, while 6.1 does not.
Thanks a lot again