Hi,
I’m trying to configure mesh (based on wired backhall) with other openwrt routers. For that purpose I’m trying using any of the wpad-mesh packages for doing so and it keep failing. It fails over an upgrade needed for ‘hostapd-common’ package, which I ain’t able to do so. When I delete it and re-install it, the router’s WIFI just looses control.
Long story short - HOW TO CONFIG MESH Flint 2?
You can’t.
Mesh isn’t supported since the router does not have the capabilities. It would be possible with some workarounds (and I mean: A lot of them) but this isn’t supported and for experts only. Since you asked how to do it … I would assume this does not fit to your current level of experience with OpenWrt.
The biggest problem: The device does not have - as far as I know - enough bands to communicate with another device at the same time while providing roaming and mesh Wi-Fi to the clients. So you would stick with f.e. 5 GHz for mesh interconnection only, but the clients can only use 2.4 GHz. Pretty useless in that case.
Only mesh possibility would be by using LAN uplink. But in that case, you can go with AP instead.
You could try to use stock OpenWrt. But then the forum for your question will change to the official ones 
My answer is that long and about Wi-Fi because other people will have the same question and might not be able to use wired connections between them.
About the bands, alot of mesh systems are dual band. Look at eero or deco. Very few are actually tri band.
Something like batman-adv should do this fine.
I answered this in another thread yesterday.
https://forum.gl-inet.com/t/cant-install-wpad-mesh-openssl-on-mt6000/36802/7
With the GL.iNet firmware I think you should be able to do what’s shown in the second video. But of course you shouldn’t disable DHCP on your main router.