In this thread Unifi 6 LR Issues - #23 by darkm4n I described some issues I had which I believe are because of this newer hardware revision and I believe I've now fixed the "bricked" u6 lr, and figured out what happened. After taking it apart and soldering on some pins to access the serial connection, it turned out the bootloader and openwrt were both mostly working fine, just that even the bootloader was unable to initialize the ethernet port, so it was unable to perform the normal tftp recovery. I was able to use the serial terminal to enable the wifi radio, use the wireless network to scp over a backup of the mtd2 and mtd3 partitions (uboot and uboot_env) from my second working u6 lr, apply them, and then the tftp recovery worked as normal. I believe that the issue was I had flashed the stock 6.0.21 firmware. Given that my to u6 lrs came with 6.0.24 and 6.0.25 (neither of which is available for download from the unifi website), I'm guessing that 6.0.21 is from before the v3 hardware rev, and doesn't support it's hardware differences (which I believe is perhaps also why the led wasn't behaving correctly either). It might be good to change the wiki page somehow to warn others of this particular risk and to avoid flashing older firmwares unless you know you have a v1 or v2 device.