Comment 5 for bug 1881207

I can reproduce this with a VM using the emulated 'e1000e' device, and unfortunately this is still a bug with upstream systemd code. I'll look at fixing this upstream but for now as a workaround, I'd recommend manually setting the mtu and ignoring the mtu from dhcp, for example by modifying the netplan yaml as such:

network:
  version: 2
  renderer: networkd
  ethernets:
    eno1:
      dhcp4: yes
      dhcp4-overrides:
        use-mtu: false
      mtu: 9000