Hi,
I have tried unsuccessfully to use openwrt on my C7 router, without any success.
The installation process fails even if users reported it as working.
|Firmware Version:|3.15.3 Build 180305 Rel.51282n|
|Hardware Version:|Archer C7 v2 00000000|
I'm sure it's an easy fix, but i need a little hand holding. Sorry ab it.
I'm not sure how you're trying to install it, but TFTP installation with the Archer C7v2 has been robust over the years that I've owned them.
I can't comment on the OEM GUI, as I haven't run TP-Link firmware recently enough to recall.
this walkthrough has the workaround (upgrade to special image of dd-wrt then to openwrt):
http://www.wolfteck.com/2018/03/25/openwrt_on_late_serial_number_tp-link_archer_c7_v2/