Three years ago, I bought the Xiaomi AIoT AX3600 Router. Back at the time, only the Chinese version was available, and that one only supported Chinese as an interface language for the admin panel, which isn’t great. Time passed, and the international variant came out. Both versions have different firmwares, so the Chinese version remained pegged to the Chinese interface. Luckily, someone over at OpenWRT found out that you can install the internation firmware on the Chinese variant. The firmware is available over here.
$ sha256sum miwifi_r3600_all_6510e_3.0.22_INT.bin 67881cea85f8452bb63b3067d3100796a9c1b4f65aaa3479dcb4d01216bc6ce4 ./miwifi_r3600_all_6510e_3.0.22_INT.bin
Once you install it, you’ll have an option to change the language to English.