Flash Archer D9 (possible?)

Hello here,

I have an "old" TP-Link Archer D9 that I want to flash with OpenWrt. The device is currently running the last firmware version released: Archer_D9_v1_150826
I followed successfully the guide publish on [here] (https://openwrt.org/toh/tp-link/archer-d9) and I'm able to "flash" any image skipping RSA, MD5 signature. Problem comes after image is "flash". I wrote flash both times in quotes because I think NOTHING is happening on the background. If I don't apply the patch I directly get an error refusing to even load my image. After applying the patch I can load it and the normal progress bar appears. It makes me wait saying that is rebooting but once all the process finishes nothing happens (apart from httpd server dying). I reboot the machine through telnet, power, reset to factory... nothing, it always come back with the tp-link firmware.
I know that maybe the device is not fully supported (in terms of modem capabilities) but it's not what I'm after. I just want the routing/wifi capabilities and I think that's possible. Unfortunately I'm unable to flash anything into the device.

Any help or guide will be much appreciated. If I end up bricking my device it's "fine" if this doesn't work I'll end up buying a new one anyway, so nothing to lose really :wink:

Thanks!

excellent!... what offsets/pid did you have?

It's uncertain currently whether the offsets to patch are the same across devices, however listed here is the patch and code from one device