So Moxie backtracked and says they'll push a fix to make pins optional. Meanwhile if you don't add a pin (which the app still doesn't say will /upload your signal contact list into the signal servers/) you can't get back in to coordinate a platform switch with your secure contacts. Unless you were already using the desktop app which isn't pin locked, or somehow manage to downgrade the phone app.
Suddenly being held data-hostage -- turn over this data or you can't talk to the people, not even to arrange a different means of contact -- without any forewarning is unacceptable and a perfect example of why centralized infrastructure and single-client rather than interoperable systems are a major failure.