My understanding is that CPU firmware is published by the CPU manufacturer, but that they will only provide updates to the PC manufacturers rather directly to than end users. The PC manufactures then push it out to end users, I assume they will have some proprietary tools for installing it - similar perhaps to a BIOS update.
In the case of Apple, the OS vendor and PC manufacturer are one and the same, which may make things easier. I see no technical reason it could not be incorporated into Apple’s usual software update channel, though I do not know if that would be too complicated, or if they have actually done so, in this or any other case.
When I saw mention of hardware support being needed, I had visions of board-level chip swapping, hence my puzzled response. And my alarm too, as Apple customers are generally not meant to swap chips. I can cope with a solution that involves new firmware/microcode, which is most certainly, in my book, still ‘only software’.