C50 v1 appeared from 2015, and is a model with 2 external aerials
C50 v3 and v4 (and v6) are white models with 4 external aerials.
C50 v5 and A5 v5 went on sale from 2018 and are similar in style to original v1 model with 2 external aerials. I have corrected the mistake in the first paragraph of the openwrt wiki page which incorrectly stated it has 4 antennas.
OpenWrt wiki page does contain instructions for C50 v5 and A5 v5.
For v4 and v5 models, you MUST build your own 'install' image as detailed in the Openwrt wiki, to convert the router from OEM to OpenWrt. Links to prebuilt 19.07.3 install images are also available in the wiki page which you can try at your own risk.
https://openwrt.org/toh/tp-link/archer-c50#v4_and_v5_instructions
See also:
https://forum.openwrt.org/t/archer-c50-v5-us/52660
https://forum.openwrt.org/t/archer-a5-v5-installation-help/68647