mwan3 can do the job. But you need to configure this by yourself.
First disable repeater manager by comment out gl_health in /etc/rc.local because it only manage one sta.
Second set up multiple STA connections.
Third, configure mwan3 which is already installed in the router. You can refer to openwrt wiki page for help. Generally the task is to write a working /etc/config/mwan3 according to your network configuration.