Flash OpenWrt (FRITZ!Box 7362 SL)

Connect to device via lan port and assign static ip 192.168.178.2.

Download initramfs-kernel and flash script

wget http://downloads.openwrt.org/releases/19.07.6/targets/lantiq/xrx200/openwrt-19.07.6-lantiq-xrx200-avm_fritz7362sl-initramfs-kernel.bin
wget https://raw.githubusercontent.com/openwrt/openwrt/master/scripts/flashing/eva_ramboot.py

Power on the device and execute the flash script shortly after (1-2 seconds):

python3 eva_ramboot.py 192.168.178.1 openwrt-19.07.6-lantiq-xrx200-avm_fritz7362sl-initramfs-kernel.bin

Wait until OpenWrt starts in recovery mode (Blinking red power LED)
Remove static ip and let DHCP assign you one (Or change to 192.168.1.2)

Download sysupgrade image and transfer it to the device:

wget http://downloads.openwrt.org/releases/19.07.6/targets/lantiq/xrx200/openwrt-19.07.6-lantiq-xrx200-avm_fritz7362sl-squashfs-sysupgrade.bin
scp openwrt-19.07.6-lantiq-xrx200-avm_fritz7362sl-squashfs-sysupgrade.bin root@192.168.1.1:/tmp/sysupgrade.bin

Establish ssh session and execute system sysupgrade:

ssh root@192.168.1.1
sysupgrade /tmp/sysupgrade.bin

If you’re having trouble timing the flash script (ftp server is only accessible a few seconds during boot) you can try this little hack:

Timing issue workaround ↕

Download the FRITZ!Box recovery tool of a different device (e.g. 7490):

wget http://download.avm.de/fritzbox/fritzbox-7490/deutschland/recover/FRITZ.Box_7490-07.21-recover.exe

Start it via wine (or in windows) and follow the instructions:
```
wine FRITZ.Box_7490-07.21-recover.exe
```
When the tool tries to flash the recovery it will tell you that you’re trying to flash the wrong recovery. However the device won’t boot and the ftp stays accessible (Don’t close the window!).
Now you can proceed to execute the flash script (step 3)

Sources

openwrt