https://wccftech.com/z590-motherboards-pcie-gen-4-0-compatibility-intel-rocket-lake-core-i9-i7-i5-cpus/

Two weeks from now, Intel and its board partners will be introducing their brand new Z590 (500-series) motherboards which would offer full support for 11th Gen Rocket Lake Desktop CPUs. The key feature of these boards aside from the next-gen CPU support would be advanced I/O features and full support for PCIe Gen 4.0 protocol.

The information comes listed on several Z590 chipset based motherboards that we have started receiving from board partners ahead of the 11 January announcement. Each motherboard has a sticker on the top PCIe slot which mentions that the Gen 4.0 protocol will be supported by Intel's Rocket Lake Desktop CPUs.