Julia kernel on JupyterHub system-wide LDAP

I think you can use the JULIA_DEPOT_PATH environment variable (documentation) for that. If you set this to a globally visible location (e.g. /opt/julia-depot or something) when installing IJulia from the console, it should install everything there. For the ldap users, you then need to make sure this path is appended to JULIA_DEPOT_PATH, since the first entry is expected to be a user-writable location.