This does not appear to be officially supported. On top of that, it appears to require one to use Xiaomi mobile software and accounts to set up the router initially prior to any flashing.
The "3G" model is not the model you linked. The 3G model requires you to flash proprietary firmware and then associate the router with a Xiaomi account using mobile apps for God only knows what convoluted reason. I would not trust this router even with OpenWRT running given the amount of blobs it requires and the hoops Xiaomi makes you jump through in installing an aftermarket OS.
https://www.aliexpress.com/item/Xiaomi-WIFI-Router-3-ROM-128...