Archer C50 uses Mediatek SoC and someone said me that this chipset is
improving a lot recently. So I suggest you to try snapshot or wait for
the upcoming openwrt 19.07 release to see the improvements.
But our interest on this router is to setup on *private network* part
of the community network; just a (good) Access Point. Similar devices
I don't imagine an scenario where you want to mesh with Archer C50, it
is for a cheap event or big building installation? Can you cable
everything and put that routers functioning as access points with a
shared DHCP server?
Phicomm KE 2P (someone has to work on compatibility for openwrt, cheap
in some of the shops)
WR330 MTK MT7621A (already comes with openwrt)