Hi,
I'm noob with OpenWrt, In list available firmware I can see the Archer mr200 but not the Archer mr400. Is it possible to try to install the mr200 firmware ? is it possible to easy customize the mr200 firmware for mr400 ?
Second question I try to use the mr400 for access with voWifi, the router access to internet with simcard. This function is not supported by original firmware (do not reply to ISAKMP and ESP message). OpenWrt can help for this ?
In general, you can't install firmware for one embedded device on another, even if they have the same chip set. Trying to do so may destroy unrecoverable, instance-specific data in the flash (and potentially other problems).
If you have basic C and shell skills and access to a Linux-based development box (or VM), then you could try to port OpenWrt to the device (assuming the hardware is compatible)