update-torbrowser
is broken in the whonix-ws-16 template as of tor browser 12.0. This problem appears to be due to a Tor project change in URLs. The latest files are now located in the following directories:
https://dist.torproject.org/torbrowser/12.0/
http://scpalcwstkydpa3y7dbpkjs2dtr7zvtvdbyj3dqwkucfrwyixcl5ptqd.onion/torbrowser/12.0/