Two cores are fine. Memory depends on how much you can spare and what kind of additional AddOns you run. 3G, 4G should be plenty.
I usually run most of my stuff in Linux Containers but HomeAssistant is still a VM. There is a script that just creates you a VM with HomeAssistantOS. Runs great!
Edit: Forgot to link the script… Installing Home Assistant OS using Proxmox 8
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