Packages are published as GitHub release assets. Add to /etc/pacman.conf:
[lx2160] Server = https://github.com/archlinux-lx2160/pre-built-packages/releases/download/latest
incus remote add archlinux-aarch64 https://archlinux-lx2160.yxio.net/incus --protocol simplestreams incus launch archlinux-aarch64:archlinux mycontainer