Doesn't that just offload the backdoor potential to the FPGA rather than a CPU?

I think it would be impossible, from a computer science standpoint, to create a backdoor in an FPGA that could compromise your own OS, in a general case. Perhaps, the computer that you use to program the chip could be compromised, to change the code that is put on the FPGA.

When I wrote that, I was under the assumption that people would use open-source CPU designs from OpenCore for convenience. With a little help from Xilinx and Altera, it wouldn't be too hard for a government to have the synthesizer detect when an OpenCore design is being used and surreptitiously put a backdoor in. I admit that it would be hard to write software to simultaneously detect a completely unique CPU design is being synthesized, figure out its instruction set and weaknesses, and finally create a hardware backdoor that could circumvent any software written for that device.

As always, there's a tradeoff between cost and security. How many hardware hackers are good enough (or motivated enough) to design their own brand new ISA and CPU design, then bootstrap a compiler and OS for their homemade CPU? Maybe 0.001% of the population, if that.

Well, I'd be down to try at somepoint, if I knew where to start. I feel like moving forward from now, in general, the future will require these skills in order to maintain some sovernty over onself.

I was wondering about that too. So we're down to buying silicon wafers in the the mail, 3d printer or some set up to dope them using open source designs? Is this possible now?