Transportator, KR,
If you first read https://openwrt.org/toh/xiaomi/ax3600
There is mentioned how to obtain and install OpenWrt.
Make sure to know which specific AX3600 version you have, it is stated that there are 2 different versions of the same device.
For first use, I recommend the Firmware-Selector of OpenWrt as the first approach.
As for a snapshot version of OpenWrt I see 2 different AX3600 versions (Platform: ipq807x/generic or qualcommax/ipq807x)
Also good to know is: Adding OpenWrt support for Xiaomi AX3600 (Part 1)
As the latest OpenWrt version seems to be the first working version for this device.
Next you could build your own OpenWrt firmware with your specific packages in it.
DG.