Install OpenWrt firmware in qca9531

You can easily install this in your described hardware.
See this Routers with QCA9531
You can install one of them in this router, for example you can try TL-WR810N or other TP-Link models but first you need a compatible bootloader.
You can try this Breed-QCA953X
I have recently installed Openwrt on unsupported device with QCA9533 Read This Tutorial
So it is possible to install openwrt if your device have supported CPU, at least 32MB Ram & minimum 8MB of Flash, However if you want to install additional packages later 32MB Ram may be insufficient.