I think it was a DIY machine, those RTX 3090 have gotten cheaper for sure.
From my experience, going beyond 4 GPUs is a pricey affair. See [§]. All but one model of the RTX3090 require at least 3 slots.
If 4 GPUs connected via PCIe 4.0x16 are enough you can choose among various sRTX4 boards for 3000 series AMD Threadripper CPUs.
