Eh, on both boards the 2nd PCIe x16 slot only has 4 PCIe lanes - physically its an x16 slot and you can put x16 devices in it, but they will only be able to talk x4 speeds.

My board two slots PCI-E 5.0 that work as x8 to CPU if both used to x16 if only one used. As well as two PCI-E 5.0 x4 m.2 slots.

To my understanding on a consumer market there isn't much that can utilize that much bandwidth. Current consumer GPUs tap out at 4.0 speeds, but use 5.0 (probably due to "more number more better" marketing). To benefit from 5.0 for NVMe it has to be very specific access patterns.

It's only sad on Intel side because they want strong market segmentation and got away with it because AMD wasn't a competitor for years.

I think there are a surprising number of people who would use two x16 slots (not the latest generation bandwidth requirements, just the electrical connection to support older products at full speed), one for a GPU, one for something like a networking or storage card. But it makes workstation and server class offerings weaker in comparison.

Well, for that I have a board from Super Micro with Epyc in it.

NICs that can utilize x8 from PCIe 5.0 or even 4.0 probably don't usually go into consumer or even prosumer hardware. PCIe 3.0 x4 is enough for a single 10G NIC. One PCIe 4.0 x8 can handle 4 of those, double that on PCIe 5.0.

There is currently no GPU on a market with PCIe interface that can utilize PCIe 5.0 x8 fully.

Storage is probably the only area where what you get from PCIe is not enough. However, by the time such bandwidth makes sense - the price of CPU and motherboard is a drop in a bucket, and you are probably limited by more than just the number of PCIe lines.

Even on high end AM5 motherboards, they'll only run at x8/x8 (or maybe x16/x4) if you populate both slots.

PCIe 5.0 x8 has the same throughput as PCIe 4.0 x16, FWIW. So the x8/x8 configuration is very reasonable.

Sure, but outside of a few SSDs (that aren't worth buying currently, need to wait for the 2nd gen pcie 5 controllers to tame their power draw), what consumer (or enthusiast) hardware is actually using PCIe 5 right now? If you slot 2 4090s into those x8/x8 5.0 slots, they'll "only" run at x8/x8 4.0 speeds.