Have you tried to use the Asus Restoration tool?
Thank you for your suggestion.
I have tried now, but the restoration tool failes to find and connect to the ap.
I took the change and use Luci to upgrade. I had to check "force" before it accepted to flash and rebooted. But something must have failed, because when it was ready, it was still running Openwrt.
I have also tried to flash openwrt-22.03.0-rc1-ipq40xx-generic-asus_map-ac2200-initramfs-fit-uImage.itb -but the same happened: It rebooted and went back to openwrt.
Serial console access is probably required, while the device has tftp push-button recovery, it's not working reliably (with changed ubi partitions). For recovering OpenWrt, one would tftpboot an initramfs image from the bootloader using the serial console - and then sysupgrade a normal OpenWrt image. I've never tried if the OEM firmware can be RAM booted.
I have a functional openwrt on the device, but want to get back to stock firmware.
I was hoping to avoid to open the box and solder. Since the device is running openwrt, I would like to use the full access to write the stock firmware to the device, maybe with som mtd magic?
I have retried the firmware restoration tool - and this time it succeded to upload the firmware - according to the tool itself. But it still boots up in Openwrt.
If I capture the sequence with wireshark, a lot of tftp packed are transfered, but the last entries was:
105577 15.603411 192.168.1.10 192.168.1.49 TFTP Data Packet, Block: 54087 (last)
105578 15.603640 192.168.1.49 192.168.1.10 TFTP Acknowledgement, Block: 54087
105745 27.415810 192.168.1.49 192.168.1.10 TFTP Option Acknowledgement[Malformed Packet]
The last entry repeated 6 times
I didn't find a way using tftp, but I also ran out of patience and just heated up the soldering iron (and recovered to OpenWrt directly, instead of bothering with the stock firmware).
21.02.x (kernel v5.4) should not be affected by the led controller changes.