wpa_supplicant just does the heavy lifting of connecting to the WiFi network.
The WiFi device itself is handled by the kernel's brcmfmac driver, and there is the usual firmware (also requires a .txt file) or you can use something like nexmon, which tweeks the firmware (and a patched driver to use it) for using monitor mode, injection and a few other misc things people have done with the firmware.
The WiFi device itself is handled by the kernel's brcmfmac driver, and there is the usual firmware (also requires a .txt file) or you can use something like nexmon, which tweeks the firmware (and a patched driver to use it) for using monitor mode, injection and a few other misc things people have done with the firmware.