Well not everything is over, I found out that this devices shares also the same specs of TP-Link TL-WR840N v6 which is indeed supported by an older version of OpenWrt who's firmware also works with this device! Maybe this could also be an opportunity for TL-WA850RE v6 and/or TL-WA855RE v4 as what was said earlier, this devices shares the same hardware specs.
There is a thread over the TL-WR40N v6 over here.
You may not do much on this devices but at least you may get the Fast Roaming feature!