I apologize for the lack of official response. There are some reasons for that however as mentioned in the FAQ;
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Apple’s products are proprietary and it is very hard to help folks install PureOS, or any OS, on their hardware. Purism also has limited resources and spends those resources on designing and building great hardware that runs coreboot, disables Intel’s Management Engine, and provides considerably more security and privacy that proprietary systems can. Supporting Apple hardware is really Apple’s job.