Hmm, I didn't know about that repos, and I don't think my setup is better, and especially, I do get the hostname/dhcp after cloudinit is done, as deploy is done on a deploying DHCP setup).. and there are specific bits to it such as IIRC:
LVM...
Would you be willing to share the packer - preseed - cloudinit code you have? I have been trying to get it to work the past days based on https://github.com/ajschroeder/proxmox-packer-examples and while it does work, I still have some quirks to...