Linux server 4.15.0-22-generic #24-Ubuntu SMP Wed May 16 12:15:17 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
LXC 3.0
Trying to create a container with -t lxc-download is producing this output
lxc-create test -t lxc-download
lxc-create: test: utils.c: get_template_path: 1431 No such file or directory - bad template: lxc-download
lxc-create: test: lxccontainer.c: do_lxcapi_create: 1711 Unknown template "lxc-download"
Error creating container testYou need to specifiy -t download. 
That is all well, perhaps confusing is reading this blog
lxc-download
This template lets you download pre-built images from our image servers. This is likely what currently most users are using to create unprivileged containers.
and the 3.0 release notes
The following templates remain in the LXC 3.0 tree and are fully supported:
lxc-busybox (mostly used for testing)
lxc-download (download our pre-built images)
lxc-local (import locally build images (e.g. from distrobuilder))
lxc-oci (use OCI application container images)
That gave me the impression that the syntax changed
Hm, I should probably rephrase. These are the names of the files not the arguments. I will update this in the posts.
Perhaps it was just my ignorance but appreciate it, it seems to make the syntax more clear