TP-Link Archer C6 v2 support has been merged into master (~= snapshots) about a year ago already, from which the next major stable release branch (20.xy) will be cut. You're probably asking for it being backported to the 19.07.x branch - that is not going to happen. Device support is usually not getting backported to existing stable branches, newly added devices will only become available in the next stable release (20.xy.0, not 19.07.z).
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Exceptions to this rule of thumb exist, but they are relatively rare and shouldn't be expected to set precedence.