5GHz has issues, particularly with the bb-kernel build. The TI AM335x BeagleBone Black Gateway Cape has a WL1837 (2.4G & 5G). The build shows the two bands but band 2 shows no frequencies. I traced this to inclusion of /lib/firmware/ti-connectivity/wl18xx-conf.bin. I suspect this is a calibration file required for older chip sets but optional for the 1837. I am assuming no 5GHz calibration data is present in this old file. Removal of this file causes the driver to use (hopefully sane) defaults. With removal 5GHz iw now shows frequencies. It is also looks like the init script may use the wrong firmware for the “TI AM335x BeagleBone Black Gateway Cape” options, why not wl18xx-fw?
I am still reviewing this but any help from the community would be appreciated.