Hi, just tried to change the machine type to q35 but cannot get ip configurations after that and the boot stuck at :

A start job is running for wait for network to be configured

My network configuration on hardware is virtio bridged to vmbr1 and the OS is Ubuntu 22.04.

When trying to change the machine back to i440fx everything works OK. Why i happens?

q35 is a different virtual mother chipset, if your ubuntu is using predictable nic name, based on pci address,

it's really possible that the nic name have change.

maybe remove the nic first, reboot on q35, then readd the nic.

When the machine type is changed from i440FX to Q35 in Proxmox, it can lead to a change in the naming convention of the network interfaces. The interface name shifts from a traditional naming schema like ens18 to a predictable naming schema such as enp6s18.
This change can prevent the operating system (in my personal case, Ubuntu LTS) from correctly recognizing and configuring the network interface, ultimately resulting in the VM being unable to obtain an IP address.

I solved the issue by changing the interface name in the netplan configuration from ens18 to enp6s18. After identifying the new interface name using the command ip a, I updated the YAML file in /etc/netplan/ and applied the changes with sudo netplan apply. This allowed Ubuntu to recognize the network interface and obtain the correct IP address.