On raspberry pi 3 with Ubuntu 24.04 server (64bits), impossible to configure eth0

Question

With a fresh install of Ubuntu 24.04, configured through cloud init (this added wifi config, username and ssh key).

On start, the wifi is correctly configured, but the LAN interface is not configured. Impossible to get an IP from DHCP.

Adding a netplan configuration for eth0 does NOT help:

network:
    version: 2
    ethernets:
        renderer: networkd
        eth0:
          dhcp4: true
          optional: true
          dhcp6: true

Any idea where to look for a solution?