Hey, thats what I understand from this page:
https://openwrt.org/inbox/toh/xiaomi/ax3000t
There is no way to install.
New AX3000T devices with stock firmware version 1.0.84 or newer have received updated hardware (AN8855 switch) that is temporarily incompatible with the OpenWrt image until support is added. There is no possibility to install OpenWrt on RD03 for such devices,