Despite its single PCIe 2.0 lane support, the Raspberry Pi can easily identify up to 20 PCIe devices through the Broadcom PCIe switcher provided on the Seaberry carrier board. This setup enables the use of multiple Tensor Processing Units or Wi-Fi and Ethernet interfaces.
https://www.notebookcheck.net/Seaberry-mini-ITX-Raspberry-Pi-carrier-board-features-no-less-than-11-PCIe-slots-and-a-robust-port-selection.581700.0.html