gen5 does not exist in x1, that is IP issue. other issues you mention are only "firmware disabled". chipsets are capable of bifurcation, so maybe try to visit

gen5 does not exist in x1, that is IP issue. other issues you mention are only "firmware disabled". chipsets are capable of bifurcation, so maybe try to visit some chinese / russian firmware hacking forums... i found out that server and consumer icelake generation is fully "cracked" open on there for years. there you can find all sorts of "BIOS" generators which can generate "BIOS" of your liking. cheapest way to do what you describe (after fiddling with your "BIOS", "firmware") is by buying NVME HBA, which are just renamed PCIE switch ICs.... ;) brand name PCIE4 switch can be bought for 1000-1200 dollars retail, it will allow you to bifurcate to x1 but im not sure about prices for pcie5. or if you want more costly but out of box working device try looking at [ https://www.h3platform.com/product-detail/Topology/24 https://www.h3platform.com/product-detail/Topology/24 ] and do not forget that newer intel PC have USB with 40 gbps... so do you really need 25 gbps eth ? linux / BSD does not care what you transfer over USB (ETH/ipv6 encapsulated in USB)... EDIT: you can buy HBA with 8 x4 connectors. this HBA/switch is connected to your pc over PCIE4 x8... 8 times 4 = 32 =x8 port... so you get x1 speeds, you can connect only one lane on x4, etc. out of box thinking.