@flohack Wow that was quick! It worked!
BTW I have something to report with the installer. After starting the installation with the phone in recovery, the phone rebooted to recovery again while the installer was downloading Ubuntu. After this, the installer got stuck on the "Preparing system image" screen. As I noticed that my machine didn't recognize any new device connected, I unplugged and replugged the phone (this time my machine recognized the device connected) and the installer immediatly started sending the image and correctly completing the installation.