> this would solve the biggest issue with non-server motherboards: not enough PCIe lanes.

Is that a problem?

These days, you don't need slots for your sound card and network card, that stuff's all integrated on the motherboard.

Plenty of enthusiast motherboards support 1 GPU, 3-4 nvme drives, 4 SATA drives, and have a PCIe 1x slot or two to spare.

Is anyone struggling, except folks working with LLMs? Seems to me folks looking to put several $2400 RTX 4090s in one machine ain't exactly a big market. And they'll probably want a giant server board, so they have space for all their giant four-slot-wide cards.

Devices integrated on the motherboard will either connect to the cpu via PCIe or USB, lanes aren't just for PCIe cards.

For example, motherboards with multiple nvme drives often have 1 drive with dedicated lanes and the remainder multiplexed through a PCIe switch embedded in the chipset.