[Google Pixel 4a Questions & Answers] mayday175:
Ok... sorry for the delay. Yes, I can confirm the speculation going around... I accidentally bought an AN0M phone. And yes, I was fortunate enough to sell it again (and got most of my money back)... to a reporter at vice.com. And, BTW, I have bought myself another Pixel 4a... this time it is working properly.

Some background points before I finally figured out exactly what I had in my possession...

- Being unable to unlock/reset this phone, I started looking at my firewall logs to see what activity this phone was generating. I noticed the following:

- regular HTTPS requests to arcane.one. I couldn't find anything useful on or about that site.

- occasional HTTPS requests to time.grapheneos.org. This leads me to believe that ArcaneOS might be forked from GrapheneOS.

- intermittent HTTPS requests to anom.one. I couldn't find anything useful on or about that site, however the word anom led me to discover the joint FBI/AFP operation that had just hit the news a few days earlier.

- Now suspecting I had an An0m phone, I checked the calculator app... and yes, it loaded straight into the AN0M logon screen.

- At this point, I panicked and thought I could get into trouble if this device was being tracked... so I rang the police and described my situation. They said to take it to my local police station. I call my local station (being in a small rural town, it is usually unmanned) and was advised to contact the AFP (Australia Federal Police), since it was their operation to begin with.

- I called the AFP, explained again what had happened. The nice lady I spoke to confirmed that their activity with Operation Ironside had just finished and that, yes, they had supplied such phones to some of their informants. I left them my contact details and the details of the Gumtree seller who I purchased this phone from. I was hoping that maybe he would be a person of interest to the AFP, and that I would get some measure of payback for him scamming me in the first place.

- I waited a week, the AFP did not call back... so I sold the phone to vice.com, who had already contacted me about this thread.

- It occurs to me now why "ArcaneOS" was practically unheard of in the googleverse (until a few weeks ago). This was a state sponsored development and, of course, it was in the best interest of law enforcement authorities to keep the normally open-source Android code hidden to prevent this phone being tinkered with and the true purpose of this OS and app being discovered.

To everyone that helped and suggested ideas to restore this phone to normal... thankyou. Although nothing we tried worked in the end, I still appreciate the community assistance here.

To everyone that has contacted me directly to ask how to fix their Pixel phone... sorry, I cannot help you.

I suspect it would still be possible to restore this phone... you'd just need to know the right commands to do it. By that I mean, I assume the developers probably changed the normal fastboot commands to some other arbitrary words; something that would allow them to test, develop and repeatedly re-flash their phones, yet prevent us from doing likewise.

EDIT: I've added a photo of the AN0M logon screen. I did not see this originally and the calculator app was not available when I took my original set of photos... at that time I had recently done a factory reset on the phone. However, after some time a message popped up saying that Calculator was "Updated by your admin"... which seemed strange to me at the time, as this was not supposed to be a managed device.