these two routers are the same? is possible or i will brick the router?
It's never a good idea to install firmware for another router.
The possibility of bricking your router is high.
i know, there is for ax5 a openwrt firmware?
"AX" is simply a designation for a WiFi 6 device.
This is the the list of AX devices currently supported in OpenWrt...
this is the router, also named redmi ax5
As you can see in the link I posted, it is not supported.