The discussion in this post is worthy of your reference：
Jetson Nano PCIE configration - Jetson & Embedded Systems / Jetson Nano - NVIDIA Developer Forums
I have found some ICs which named “PCIe gen2 packet switch”:
ICs:
Diodes | 3port 8lane: PI7C9X2G308GP
Diodes | 6port 8lane: PI7C9X2G608EL
Diodes | 6port 8lane: PI7C9X2G608GP
Diodes | 8port 8lane: PI7C9X2G808PR
ASMedia | 7port 12lane: ASM1812I
ASMedia | 5port 6lane: ASM1806I
ASMedia | 7port 12lane: ASM1812
ASMedia | 5port 6lane: ASM1806
Broadcom | 8port 8lane: PEX 8608
Broadcom | 8port 8lane: PEX 8609
Broadcom | 6port 6lane: PEX 8606
Renesas | 5port 8lane: 89HPES8T5A
Diodes product list: Diodes 8-lane PCIe 2.0 packet switch list
ASMedia product list: PCIe Bridge Controller|ASMedia Technology Inc.
Broadcom product list: PCI Express 开关 (broadcom.cn)
Renesas product list: PCI Express® Gen2/Gen3 Signal Integrity, Switching and Bridging Products Overview
Welcome everyone to append the PCIe packet switch ICs to this topic.