In the new Proxmox VE 9.1 release this should be possible, from the changelog: >...

		mzsl 49 days ago \| parent \| context \| favorite \| on: Adventures in upgrading Proxmox In the new Proxmox VE 9.1 release this should be possible, from the changelog: > OCI images can now be uploaded manually or downloaded from image registries, and then be used as templates for LXC containers.