You could use the images at the images: with a /cloud variant or use ubuntu: remote (that has cloud-init installed), and then use cloud-init config in LXD to provision a user and a key to avoid needing to maintain your own images.
You could use the images at the images: with a /cloud variant or use ubuntu: remote (that has cloud-init installed), and then use cloud-init config in LXD to provision a user and a key to avoid needing to maintain your own images.