Hi elie.genard,
Sorry, Yocto is not officially supported and maintained by us, but our partner have the Yocto support for Jetson boards, please refer to Announcing Yocto support for Jetson Boards
It’s also not recommended to use Ubuntu on VM because flash process need reboot and VM might not detect the board. Please use the standalone Ubuntu 18.04 for SDKM.
You could provide the full UART console log for further check.