Netgear r6220 'bricked' - confusion in how to rescue

Also made no difference.

Sorry. Actually it did - the thing would time out, not complain about permissions.

$ sudo nmrpflash -i enp0s25 -f R6220-V1.1.0.114_1.0.1.img
Advertising NMRP server on enp0s25 ... -
No response after 60 seconds. Bailing out.

But enp0s25 surely isn't the name of your USB Ethernet adapter. It's usually enx<MAC ADDRESS>.

well, honestly this may be reflecting my ignorance. Its the result of:

$ ip a
...
2: enp0s25: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether 3c:97:0e:cf:00:ec brd ff:ff:ff:ff:ff:ff
...

Oh, sorry sorry - no, there is another entry there for the USB ethnet adapter

I used:

$ sudo nmrpflash -i enx9cebe80718e1 -f R6220-V1.1.0.114_1.0.1.img
Advertising NMRP server on enx9cebe80718e1 ... |
No response after 60 seconds. Bailing out.

I'm noticing you're using nmrpflash installed from apt, which is hopelessly outdated. Version 0.9.14 was released in 2020, more than 4 years ago!

Please the USB ethernet adapter with a current version of nmrpflash.

wow. I hadn't thought to check , I didn't think apt was that bad. Lesson learnt.

Will change and come back with a report later.

i do not think that is possible, 160MHz on that device.
sorry for offtopic

bad news:

$ sudo ./nmrpflash -i enp0s25 -f R6220-V1.1.0.114_1.0.1.img
Waiting for Ethernet connection (Ctrl-C to skip).
Advertising NMRP server on enp0s25 ... -
Received configuration request from b0:39:56:1a:bc:00.
Sending configuration: 10.164.183.253/24.
Received upload request without filename.
Uploading R6220-V1.1.0.114_1.0.1.img ... sendto: Operation not permitted

Also this:

$ sudo ./nmrpflash -i enp0s25 -f R6220-V1.1.0.114_1.0.1.img
Advertising NMRP server on enp0s25 ... -
Received TFTP_UL_REQ while waiting for CONF_REQ!
Received upload request without filename.
Uploading R6220-V1.1.0.114_1.0.1.img ... sendto: Operation not permitted

The router descends into a bootloop, and it just seems to be something it returns depending on where it is in that cycle. Usually its the former.

Damn !!
I didn't wait that long. I used to the behavior of the router when using windows, and I have assumed the behavior would be the same when using Linux. That is not the case.
Ok I will give it a try the next time.

You router is R6200 while my router is R6260 so there could be differences in their behaviour when flashing.

a shot in the dark by try:

sudo setcap cap_net_raw,cap_net_admin=eip /path-to-nmrpflash/

then run nmrpflash again

it uses the MTK 7615 chip which supports BW160 (I guess BW means bandwidth). Using a wireless scanner you can clearly see it broadcast a 160MHz signal. Technically it should support data rates of 1.8Gb. Could not test it because I don't have any other device that supports BW160. Anyway, I only use 80MHz of bandwidth because I live in a residential area so don't want to occupy more bandwidth than I truly need.

i know that, but not in every case it support BW160, i think is just a web interface thing in ddwrt

I also had what you described. The behavior while flashing with Linux has been different from what I'm used to while flashing with windows.