For those not following, there was an effort to add C5 v4 to master at https://github.com/openwrt/openwrt/pull/2174. However, after more than a year maintaining the PR updated, the author lost interest and closed the PR. That PR was updating existing rtl8367b driver to also support rtl8367s. That switch driver change could be what has preventing the PR to get merged.
I created a new PR https://github.com/openwrt/openwrt/pull/4010 based on the same driver @benwht has been using since 18.06. That driver is already merged into master but only for mediatek target. For C5v4, we just need to copy it to ramips or move it to generic target. Besides that, the port should be a harmless DTS+profile+leds+network change.