I’ve installed an update on my FP5 this morning. After installing and rebooting, the phone asked for a password (black screen and only option is to fill in a password of make an emergency call).
The issue is that I didn’t set up a password. I have a pincode, fingerprint and facial recognition. The pincode doesn’t work. Any possible Google passwords don’t work.
I don’t think you can use face or fingerprint unlock without first setting a pattern or a text or number based password of some kind. In any case Android should periodically ask for it anyway (mine certainly does).
I have a similar problem: My FP5 ran out of battery. When rebooting, it aks for a pin - I type in the SIM-pin and it accepts, but then it wants a pin again and I have no idea what the pin is. It is not the SIM-pin or any other I am aware of.
If you didn’t set up a password yourself could it be that this is some kind of ransomware attack? Have you downloaded any new apps right before it happened?