BIOSTAR Formally Enables PCIe Gen 4 on its AMD 400-series Motherboards | TechPowerUp
B550 motherboard guide: ASUS and AMD bring PCI Express 4.0 to everyone with ROG Strix, TUF Gaming, and Prime - Edge Up
Amazon.com: ASUS Prime Z590-P LGA 1200 (Intel® 11th/10th Gen) ATX Motherboard (PCIe 4.0, 10+1 Power Stages, 3X M.2, 2.5Gb LAN, Front Panel USB 3.2 Gen 2 USB Type-C®, Thunderbolt™ 4 Support) : Electronics
AMD has decided to block PCIe 4.0 support on all pre-X570 motherboards | PC Gamer
Some ASUS X470 and B450 Motherboards Support PCIe 4.0 | eTeknix