What is the maximum memory capacity supported by the SB860R8, and what type of memory does it use?

It supports up to 192GB of DDR5-5600 memory across 4 DDR5 memory slots.

Does this Shuttle XPC Cube SB860R8 come with a CPU, memory, storage, or operating system preinstalled?

No. It is a barebone system, so the CPU, memory, storage, and operating system are not included.

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Shuttle XPC Cube Barebone SB860R8 Mini PC - Supports Ultra 200s CPU - Max 192GB RAM - Gigabit Ethernet - 500W (No CPU/ No Memory/ No OS / No Storage)