The issue with the packaging, as far as I can tell, is that there are TWO packages for ROS6. The download link for Netgear R6 gives you plexmediaserver-ros6-binaries_0.9.7.26.548-47ad65c_amd64.deb but there is a second /dependent/ package plexmediaserver-ros6_0.9.7.26.548-47ad65c_amd64.deb. I found I could retrieve the second if I manually altered the URL in my browser. With both these in hand, and making sure to shut down the PLEX application on the RN, you then simply ssh to the NAS and:
#dpkg -i plexmediaserver-ros6_0.9.7.26.548-47ad65c_amd64.deb plexmediaserver-ros6-binaries_0.9.7.26.548-47ad65c_amd64.deb
In THAT order. When I tried to accomplish this from the web GUI, it always seemed to result in failure. :-( My suspicion is that this has something to do with how PLEX is bundled with the ROS6 releases. It's there, but it doesn't actually get installed until you try to turn it on -- and thus why the need for two packages?
MInd you, there's a .27 now, but that's how I got it to work. In fact, I just tried to download .27 and got host not found errors. Hmm... will try from home again later.