The question What kind of hardware and software are required to build an AI system? asks for hardware recommendations. However, there exists already a site, namely https://hardwarerecs.stackexchange.com, for this specific purpose. The following question What is the reason AMD Radeon is not widely used for machine learning and deep learning? should also be probably closed as off-topic, for a similar reason.
Currently, our on-topic page does not apparently say that hardware-related questions are on-topic. We even have the tags hardware and hardware-evaluation, which probably should not even exist. All hardware-related questions should be implementation-related questions, so they should be off-optic here.