It is not the download of the image that is failing:
$ lxc launch images:ubuntu/21.10 ubuntu-container Creating ubuntu-container Error: Failed instance creation: Failed creating instance record: Requested architecture isn't supported by this host
You get a different error if the image does not exist: Error: Failed instance creation: Failed getting remote image info: Failed getting image: The requested image couldn't be found
It is not the download of the image that is failing:
$ lxc launch images:ubuntu/21.10 ubuntu-container
Creating ubuntu-container
Error: Failed instance creation: Failed creating instance record: Requested architecture isn't supported by this host
You get a different error if the image does not exist:
Error: Failed instance creation: Failed getting remote image info: Failed getting image: The requested image couldn't be found