I recently purchased an rt-ac68u v3, it's in this topic firmware, it works fine, no apparent errors. I tried to use the latest available version of merlin, but the result was disastrous.
It had constant ipv6 prefix losses, but only on lan ports, on wlan it worked without problems. The problem occurred every 10 minutes or so, it was annoying. I was also having a lot of disconnects at 5ghz, this culminated in removing merlin and going back to the official firmware.
In the official firmware, rt-ac68u v3 works very well, without any apparent bug, everything flows naturally, unlike what happened in merlin, which was very disappointing, because it's sad to lose the scripts, which gave an excellent survival to the device, but there's nothing to do, version 386.7_2 got really bad on rt-ac68u v3. Is there a version older than this that works well on this model?
I'm thinking of testing other firmwares, like fresh tomato and dd-wrt. Is the installation of these two firmwares of the same type as merlin, through the web interface?