Asus RT-AC56U bricked?

I have the Asus RT-AC56U and I bricked the firmware update on one of tries to install the original firmware.
To fix it I connected my Windows 10 PC through a USB to TTL device on the GND, TX, RX.
Everything seemed to be working normally using PuTTY as a serial console, but I decided to install the OpenWRT firmware v19.07.7 and I got the output like this:

CFE> show devices
Device Name          Description
-------------------  ---------------------------------------------------------
uart0                NS16550 UART at 0x18000300
uart1                NS16550 UART at 0x18000400
nflash0              AMD NAND flash size 131072KB
nflash0.boot         AMD NAND flash offset 00000000 size 512KB
nflash0.nvram        AMD NAND flash offset 00080000 size 1536KB
nflash0.trx          AMD NAND flash offset 00200000 size 1KB
nflash0.os           AMD NAND flash offset 0020001C size 129024KB
nflash1.boot         AMD NAND flash offset 00000000 size 512KB
nflash1.nvram        AMD NAND flash offset 00080000 size 1536KB
nflash1.trx          AMD NAND flash offset 00200000 size 30720KB
nflash1.brcmnand     AMD NAND flash offset 02000000 size 98304KB
eth0                 Broadcom BCM47XX 10/100/1000 Mbps Ethernet Controller
*** command status = 0
CFE> flash -noheader nflash0
Reading TFTP Client.
- last blk -
Done. 7340032 bytes read
Download of 0x700000 bytes completed
Write kernel and filesystem binary to FLASH
Programming...copysize=7340032, amtcopy=7340032
done. 7340032 bytes written

I restarted the router by turning it off/on and now the router is not booting and I get nothing on the console.

Do you have any idea on what I can do to fix it?

Not an expert on Asus devices, but I would say you did overwrite the flash with the openwrt image, wiping the boot loader and some other things.

If that's the case, a SPI programmer would probably be the only way to recover it.

That sounds bad...
If that's the case, how do I find the previous partitions to overwrite them?

Well, you got the sizes in your post.

But ideally you'd load a whole flash dump, and if that happens, the layout comes with the flash.

I don't really know what and how to do that...
Could you guide me through the process?

I found this image that explains some pinouts:

Your link isn't working. Better replace it with the direct Imgur URL.

For me it was working, but I replaced it with the original post I found it.

This is the direct link:

Does that thread yield any conclusive information concerning the possibile pin layouts etc? Because there are still some questions raised on that picture.