I spend another couple hours tonight banging my head on the keyboard fighting a "No authority found" error in Asterisk. This seems to come up pretty regularly when I bring up new IAX trunks, but this one was an old trunk I was trying to recover. I'm not sure if this is a new feature in Asterisk 13 or what, but turns out that incoming matching rules only look at "type=user" (or "type=friend") entries. That's different from SIP channels which will match on either one. So lesson learned.