Orbi RBR50 seems stuck in boot loop

You guys really need to look up a guide for serial flashing. You don't just buy a usb-ttl serial cable and then figure out what to do. dd-wrt and openwrt usually have guides for when these things happen because they happen very frequently in the firmware flashing arena.

basically,

#1 install the right drivers for the usb-ttl, usually a "prolific pl2303" chip, so you want those drivers. newer drivers 2018+ will read cheap ones as fakes, but older drivers like older than 2017 should recognize it right. then set the rate to 115200 in device manager instead of the regular 9600

#2 download an interfacer like putty so you can interact with the serial console. both the serial and ethernet cable must be plugged in, so there are 2 cables interacting with the orbi. make sure you don't plug into the 3.3v on the serial or else you get the magic smoke. set the ip on network settings to 192.168.1.1 on gateway, 255.255.255.0 on subnet, 192.168.1.10 as the adapter's/yours. on putty, find the serial setting and turn the flow control to off and rate to 115200, and whatever com it says (copy the settings from device manager), then in the connection type click serial, host as 192.168.1.1 on port 69 (because netgear does port 69 on orbis for whatever reason)

#3 click open to show the interface and then power on the orbi. if nothing shows up, you prob need to switch tx and rx pins. you likely need a multimeter to know 1. which is ground first before 2. knowing what hot/3.3v is so you don't plug anything into that one. if you do it correctly, it should shove a whole lot of info on the console. to stop it all push ctrl c or any other button I think.  type in "help" to show all the options, but you very likely only need "fw_recovery" and a tftp program to send firmware into it. If none of that works and the u-boot is corrupted, then all this effort was wasted and you likely need another rbr50/rbr40 with a good uboot to extract from and reflash. Unfortunately netgear does not provide bootloader download, nor does anyone else on the internet. At least, not yet.

That's probably most of it and you can probably find other missing info from the other serial unbricking guides. If you bought one off ebay just to try it, you're really gambling. Just like my dumb dumb butt. So far, I have had a 70% success rate with the other 30% being bad uboot.