This is a workaround for lxd snap installer working with network restricted installs using Juju versions prior to 2.7. 2.7 is the first version of Juju that has updated code to handle lxd from a snap source and is, hence, working in a better way.
Previous Juju versions used to get lxd from deb.
Using 2.6.9, with a manual provider install on s390x lpars, I had to:
after this the containers came up