I am having the same issue with a newer FPGA. The MAX 10 FPGA. I can not place an order because the vendor sates Intel will not take backorders.
Although on this webpage Intel seems to state the chips will be available until at least 2032.....
Low Power FPGAs: Intel's Edge-Centric FPGA Overview-Intel
BOTTOM OF PAGE
"Why is Intel extending support for these FPGAs until 2032?
We realize that customers choose to deploy with FPGAs because of the ability to be supported for 15 and frequently over 20+ years. With over 2.5 billion MAX® and Cyclone® FPGA devices sold, it’s important that our customers realize that they can continue to rely and design in confidence with these widely used FPGAs."
Perhaps someone from Intel could explain when these chips will become available for purchase?