I'm not even sure if this is the right place to post this experience for feedback. Lacking a better idea, here goes...

I booked 2 business class (D) tickets directly on AA.com from HKT to DOH in May for travel this December. I received a flight change notification from AA advising me they were unable to rebook. I called and they said the flight was no longer available but I could book one 12 hours earlier leading to a very long layover. I checked Qatar Airways website and found a direct flight with a new number but leaving 5 minutes earlier than my original ticket. AA tells me there is no availability on that flight (QR did not release codeshare to them) and my only recourse is to travel 12 hours earlier. I can book the desired flight directly on QR.com but of course now the price is 3x with many seats available. It appears they are very confident they can sell those seats themselves and no longer need the AA codeshare but I'm pretty frustrated. Since I already purchased the ticket when there was a codeshare, I think I should be rebooked on the new flight regardless of QR avarice. Maybe I am missing something. Any insight or advice?

The AA or QR forums would be better choices I think. As this is an AA ticket I would start in the AA forum; when an airline cancels or loads a new flight it often takes some time for codeshares to be reattached or made available. I would give it a few days and see if the codeshares for this new flight number are reestablished. See for example:
What are my rebooking options for a cancelled codeshare flight

Qatar takes back 3rd DOH-JFK frequency previously operated by AA