Which is to say, every system in actual widespread use. All such CPUs, GPUs, storage devices, displays, etc. run closed microcode and firmware. It'd be funny if it wasn't so profoundly sad.
And even if they didn't, the silicon design is again, closed. And even if it wasn't closed, it's some fab out somewhere that manufactures it into a product for you. What are you gonna do, buy an electron microscope, etch/blast it layer by layer, and inspect it all the way through? You'll have nothing by the end. The synchrotron option isn't exactly compelling either.
I'll just highlight this excerpt of your own words for you, and usher you to evaluate whether your position is even internally consistent.
Trusting someone doing the right thing when you purchase is different from trusting them not tampering things remotely in the future. Companies can change management, human can change their mind. The time factor is important