I finally got my GL-AR300M-ext (note don't go looking for special firmware for an -ext model; I finally realized in a "duh" moment that this only means you have external antennas). I kept loading all versions of firmware (switch was switched to NAND or leaning toward the USB port) and anytime I would load firmware, no matter how large or small, I'd start for booting into uboot, and I found that one green light and the opposite red light would start flashing and I would need to release the reset (set before power on) button after the 6th flash which would give solid red and green light and ready to load from Windows "Edge" seemed best, although it required a clearing of browser history a couple of times and of course after setting to 192.168.1.2 and 255.255.255.0. The red light would always flicker with the initial upload of firmware and then I'd get the "other" green light flashing in unison and with such dim in tensity it was barely visible as both the red and "other" green light flashed once about every 15 seconds. With a couple of the smaller firmwares I loaded, it actually looked like a traditional firmware load since after a while the red and "other" green light would show flashing maybe after a couple of minutes of the upload. But I could not even ping the 192.168.1.1 address after this firmware gave the appearance of loading. I gave up and read a lot and I have to admit, I (at this stage of my post-IT career) don't want to get into loaded memory locations, so figuring the half-Franklin I would be out if I bricked it, I just decided to try some random things I'd read elsewhere, so I flipped the switch away from the USB connector and loaded the newest uboot from here after learning it didn't seem to load from the other switch position:
Once I loaded that, I flipped the switch back toward the USB connector and I tried uboot again to load a recent version of Rooter and it performed as I remember my other GLinet routers did with the correct wait after upload and flashing of lights and voila I had a luci menu.
I don't know what I did but it seemed to work and maybe someone else can try this too if you don't want to do exercises in Linux memory locations and the other tedious education requirements of Uboot, etc. Best of luck!