I inspected Radxa CM5 schematic and pinout. My conclusion:
You will need a custom adapter board (and some hacks) to enable Wi-Fi support.
Unfortunately, Radxa CM5 does not route SDIO to its module connector, but it has an extra PCIe lane broken out.
There is two way to support Wi-Fi.
One, less hacky way: Break out an extra PCIe lane and wire it to m.2 2240 slot. Then plug in off the shelf Wi-Fi module.
Two, super hacky way: Desolder the Realtek Ethernet PHY from the module, wire jump wires over it, connect those pins to Wi-Fi module using custom adapter board.