I also work with many .com.ar domains.
Obviously is not a definitive solution, but what I did was to replace line 32 in trellis/lib/plugins/filter/filters.py.
from
if len(host.split('.')) > 2:
to
if len(host.split('.')) > 2 and ( ('.').join(host.split('.')[-2:]) != 'com.au' ):
Let me know if that works for you.
I’m not python expert but digging into this problem I found a plugin which might help with this issue. https://github.com/john-kurkowski/tldextract