The CM4 IoT Router Carrier Board Mini is a great little board, easily capable of handling gigabit routing with OpenWRT. But the stock Raspberry Pi images from OpenWRT won't work, because an additional driver is needed for the second network interface. Luckily, the OpenWRT team has made it very easy to build custom images.
Go to the OpenWRT Firmware Selector, choose the Raspberry Pi 4B/400/4CM (64bit)
model, then open the twist-out to "Customize installed packages"
Add these packages:
bcm27xx-userland brcmfmac-firmware-usb kmod-brcmutil kmod-cfg80211 kmod-r8169 kmod-usb-dwc2 r8169-firmware