http://l3tczdiiwoo63iwxty4lhs6p7eaxop5micbn7vbliydgv63x5zrrrfyd.onion/4.0.0/user-manual/config.html
Unencrypted connections to systems in these address ranges will be as (un)secure as the local network
is, but the alternative is that you can't reach the local network through Privoxy at all.