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The Late 2012 Mac Mini Server makes a cheap Proxmox VE node and is the last fully upgradeable Mac Mini. Its two SO-DIMM slots support 16GB of RAM, and its two 2.5-inch SATA bays can hold a boot disk and a datastore. Apple soldered the RAM in 2014 and moved the line to ARM in 2020, so newer Minis either cannot take more memory or cannot run x86 virtualization.

Its quad-core mobile Ivy Bridge i7 keeps power use modest for four cores. The whole machine is a 19cm-square box that fits on a shelf.

Making a macOS USB installer becomes awkward when the host and target use different architectures or macOS generations. I ran into it while reinstalling macOS 10.7 Lion on a 2012 Mac Pro from an M1 MacBook Air. The M1 cannot run Lion's installer, and Apple's direct Lion download is packaged in a form that modern macOS refuses to open.