It worked, I could ssh to it, but with the lack of LuCi and no easy way to enter the PIN code of the SIM card with the CLI, I wanted to switch back to the latest firmware (TL-MR6400v5_1.3.0_0.9.1_up_boot(201207)_all_2020-12-08_08.39.09.bin)
I renamed TP-Link's firmware file to "tp_recovery.bin" and served it with TFTP on 192.168.0.225, as mentioned in the instructions
When using the latest firmware, if I used the count=16000 parameter, the router was also bricked
So I used this dd command, just to try: dd if="TL-MR6400v5_1.3.0_0.9.1_up_boot(201207)_all_2020-12-08_08.39.09.bin" of=tp_recovery.bin bs=512 skip=1
No "count" parameter as you can see. And then, it worked!
I don't think this knowledge is available anywhere, so I took the time to create this post...
In short, the first 512 bytes of the TP-Link firmware have to be ripped of the image served by TFTP, but no "count" restriction seems to work. Hopefully, I am quite knowledgeable with TFTP and DD as well as with embedded firmware/software.
I just hope this could help someone else in the future
Seem you successfully get your modem connected... i checked my ifconfig same as yours...
the weird thing is we dont get MAC ADDRESS... so far i dont get any errors...
here i attach my compiled stable 21.02.0... plus it has scripts for WAN & SIGNAL STRENGTH led..
hope you can give a try....
I'm using your compiled firmware on my MR6400 v5.2.
I installed via tftp and works good even with signal leds. But there is a glitch. I'm not using this router always.
And whenever I need to use I had to press reset button on back or login with luci and reboot. Because if I didnt these no signal leds and no internet connection established. I see NETWORK_REGISTRATION_FAILED on QMI section.
Do you have any idea to solve this ?
Not: I'm using Russian MTS sim card in Turkey just for testing. Router will go to Russian next week with this sim card.