Not Rocket Science » Adding multiple devices to one PCI Express Slot
B550 motherboard guide: ASUS and AMD bring PCI Express 4.0 to everyone with ROG Strix, TUF Gaming, and Prime - Edge Up
Here's an insanely long motherboard with 8 PCIe x16 slots | PC Gamer
Amazon.com: ASUS AMD AM4 Pro WS X570-Ace ATX Workstation Motherboard with 3 PCIe 4.0 X16, Dual Realtek and Intel Gigabit LAN, DDR4 ECC Memory Support, Dual M.2, U.2, and Control Center :