Just download this binary, and rename it to firmware.bin (If the name is too long, it can't upload to the router)
How can I check to official firmware version? -> Go to admin page, you can easily find it.
Download link here: Archer C7 OpenWrt
For v2.0 official firmware:
We can dirrectly use the official admin page to upload the openwrt firmware (suggest, extremely easy flashing)
Then just wait for a while for the uploading... done.
Update customefeed.conf then do opkg update and install
vi /etc/opkg/customfeed.conf
src/gz openwrt_luci2 http://downloads.openwrt.org/snapshots/packages/mips_24kc/luci/ # Add this line, save & close
opkg update && opkg install luci-theme-rosy