How can i install openwrt on Xiomi ax1800 chinese box version?

My router name not included the openwrt supported device list but it's capable to install openwrt, how can i install openwrt on my wifi 6 supported xioami ax1800 box china version router.
The router picture

This means it is currently unsupported.

What do you mean by this? How do you know it has that capability if OpenWrt doesn't support that device?

You can't. At least not now. You could put in a request into the developer section for support to be added for this device. The ability to support the router depends on a number of factors -- namely the processor and chipset that is inside, firmware/boot loader that doesn't prevent OpenWrt from actually being installed, the availability (and to a degree, the popularity) of the router (the devs need to be able to test against the actual hardware), and a number of other things. If you are a developer (or have appropriate software engineering skills), you could help bring support to this router.

Gearbest review

In terms of chips, Xiaomi Mi router AX1800 uses Qualcomm enterprise-class 5 core chips-Qualcomm IPQ6000, applies enterprise-class chips to home routers to ensure the stability of the network at all times. The computing power of 4-core 64-bit A53 1.2GHz CPU+ single-core 1.5 GHz NPU, is as high as 11040DMIPS.

IPQ6000 developer thread:

There is very little chance for ipq60xx support in OpenWrt within a reasonable time frame, even less for ipq6000 (in contrast to ipq6010/ ipq6018).