The code to support the GL AR300M16 is in the nightly builds, available from May 18th, 2019. Summary of specs:
* 2GHz
* comes with or without 2 external antennas models
* 23dBm max xmit power
* 2 ports - LAN/DtDlink (untagged/vlan 2) and WAN (untagged)
* power is supplied with USB 5v cord (could run for days on readily available battery pack typically used to charge cell phones)
* look for the "gl-ar300m" image
* 3 led lights: power, booting/booted, established mesh link