I was wondering what was going on here:
apt -o Dir::Cache::Archives=/home/phablet/anbox install anbox-ubuntu-touch
On Telegram zubozrout explained that :
"Well all it does if I parse it right is that it downloads the packages to a specified folder instead of the cache folder on the root filesystem (if you pick a folder in your home for instance) and then installs it from there. So it may not help if the rootfs is too full since the installed files end up where they should anyway but it saves a small part needed for the actual download which may allow you to install it."