What would the enclave do for you if you're running an OS that doesn't support Apple Pay or Touch ID?
It is used for the camera too.
On Thinkpads you can disable the routing of signals of the mic and camera in the firmware. Afterwards, it's not available to the kernel. Whether that's somehow hackable via a UEFI bug I don't know, but there are also laptops with physical switches the mic, wifi and a lid for the camera. Your safest bet is to open it up and disconnect the device, which is less likely to raise alarms on Linux and BSD than it is under macos, I assume.
Build your own? Its an ARM chip running a relative of SEL4. Would be an interesting project.