First of all switch to Incus. Read this comparison between LXC and LXD. Incus is a fork of LXD. One reason to choose Incus over LXD is for better access to alpine images.
I started with LXD myself, so I don’t really know the differences from LXC.
Incus has commands to publish, export, and import images. It also has a way to share images via its https interface. I prefer to share images by manual export-copy-import, so that the Incus instances are independent.