the original thread for the MiWiFi 3C (Support for Xiaomi MiWiFi 3C) was closed because some users had misused this forum for discussing other firmwares than OpenWRT.
There is an easy way to gain SSH access to the router without opening the case.
By this it is possible to install BREED for flashing firmware.
The system architecture of the Mi-Nano is quite similar to the Mi-3C.
So I have taken the firmware of the Mi-Nano and flashed it via BREED.
Everything works correctly with the 19.07.5 firmware ... except that the WAN and the LAN1 ports are interchanged.
So it should be a small thing to do the required adaptions for having an official OpenWRT release version for this router.
Is there anyone who wants to support?
I have already re-engineered the correct port assignments and need someone who has the authority to put those into the configuration file.
I have updated the Wiki on how to gain SSH access, how to flash BREED and how to install the firmware: