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...
If you ever need to find out again how the Drives map (mostly they are numbered the same, but don't count on that), you can just run lsblk -S
The Serialnumber contains the numbering from Proxmox (drive-scsi0/1/2 etc..)
$ lsblk -S
NAME HCTL...