I did a simple install on a new Proxmox host a month or so ago. You may find this thread helpful - https://forum.alta.inc/t/install-alta-control-in-proxmox-as-lxc/3794/6
It’s basically just a case of creating a Container Template using the root FS file, create the container using that template, then I just resaved the network settings for the container in Proxmox as it didn’t seem to have them initially. That was it. Was then able to go through the setup process at the IP address to get the Local DDNS link etc.
It found all my new Alta devices just by using the standard Proxmox virtual bridge network. Been running fine ever since!