To be clear.
As @robimarko and I have attempted to articulate...it is dangerous to the modify those chopped-up BIN files, and attempt to reflash them like the originals. I think that's what is unclear here in your belief that this community doesn't understand reverse BIN file engineering.
There's more process involved; and it's easier to use the proper firmware build tool to make the firmware file - if you are already aware of those particulars.
Ok, im just here to drop the fix i have to these repeater..
im using openwrt on a xiaomi r3p with 4 of these repeater around the house.
to make it work as a repeater to the r3p with openwrt on, is before you install openwrt into the router,
make everything work correctly before moving onto openwrt, what i mean is install you router as normal with xiaomi app on phone & settings etc etc, and link these repeater to the router and make sure its working.
then all you have to do is install openwrt to the router with the SAME ssid as you setup in xiaomi firmware on the router, then reconnect the repeater to the power.
the repeater will reconnect to the ssid with openwrt on. you can check it with the xiaomi app (if you havent uninstall it)
Were you able to change the firmware of your repeater؟
I also bought one But I don't like the firmware and I want to change it
I don't know if that is possible or not 