@dollop Seems that the router supports the OneMesh only in router mode :( there is no support in access point mode (very strange decision) https://www.tp-link.com/en/support/faq/2690/ Q7. Which mode...

There is no support for OneMesh feature in the latest firmware for the router in spite of the fact that this router (Archer C6U V1) is marked as compatible with the TP-link OneMesh in the product...