I can't say I've tracked the versions of RMP.. but I don't recall the new icon.. so I don't know if this is inherent with RMP 5.x or just this latest version.
But.... it is *almost* impossible for our TVs to find our QNAP now for playing videos. This was rock solid for 2+ years.
*IF* I click on the Video/All/Help buttons enough times, the QNAP will finally show up.
Tried from 2 Android devices, and from the QMedia Roku app.. all of those found the QNAP immediately.
I prefer the UI on RMP vs. Qmedia.. but working-and-ugly is still better than not-working.
I don't see any reason for RMP to not find any DLNA player, but I'd recommend trying Plex on your QNAP if it has that as an option.
You should report this to Roku:
You might consider joining the RMP beta program (send a message to @RokuChris) - the RMP beta app is currently at 5.4.2 as well..