BTW. Perhaps I should mention that I have a somewhat crude solution that seems to work for me.
What is especially important is to not accidentaly add / in front of paths. Doing that as root at the wrong moment will definitely do bad stuff with your pvehost.
Use it at your own risk or improve...
In my testing I have only used LXC templates provided with pveam.
I have found oddities in the filesystem layout for some LXC templates from proxmox.
I have not tried all other templates but the ones where I have found the oddities are theese.
debian-10-standard_10.7-1_amd64.tar.gz...