OpenWRT Router working with TP-LINK OneMesh™ device

Hardware Questions and Recommendations
1

Hello everybody!
I am glad to join OpenWRT Community!

I have Tp-Link Archer C7 ver.5 (AC1750) and TP-Link RE 300 in OneMesh™ configuration. The router itself started to drop-off Internet connection and also, on random basis, some of the devices, connected to LAN could not resolve DNS server (either through wi-fi or cable). Nevertheless, I heard from a friend for the OpenWRT option for my router. I have just installed it and now it seems stable.

Although after Open WRT installation router signal is better, there are still some spots in my apartment with low signal coverage. Too much concrete in the walls. So, I need to add TP-Link RE 300 device in mesh configuration. Since there is no OpenWRT version for that extender, is there a way that I could Mesh TP-Link RE300 using manufacturer's official firmware with my Archer C7 Router that has OpenWrt 19.07.5 r11257-5090152ae3 / LuCI openwrt-19.07 branch git-20.363.66498-eb2cc80 installed?

Thank you in advance!
Be all safe and healthy!

2

I have come to the same problem, and as far is I know everywhere I search about this matter ends up on that TP-Link has done the mesh setup on their own way (not over the standards of the industry)
So there is pretty much no chance to replicate the OneMesh setup on OpenWrt so the range extender thinks that it still talks to a TP-Link original setup router.
Some people has cut some corners and they installed OpenWrt firmware on their range extenders so they can setup a mesh network with OpenWrt ways, unfortunately this isn't my case because since I have two RE205 v3.0 that there is no firmware support for them on OpenWrt. Also I have tried with some old TL-WA855RE v2 since there is a firmware of OpenWrt but for the v1 version but without any luck yet.