I have the Same issue over here. Joined because I thought I could download the 0.9.10.3 for my qnap arm device. (ts-412)
The last message on this forum about this issue is october 6 'where are looking into it'
Lets hope this solution comes out in the very near future.
However I relented and installed the PC version of media server on my desktop (not my preferred choice), but for the time being it works a treat and with the limited use that I've already made of the Xbox One Plex App I'm pleased with it, doing what I want easily and smoothly. (Used the Serviio MS on my TS-419P II since buying it a year ago). Especially now that I can get rid of another remote and control Plex using voice (or gesture)! No more do I need to swap to another configuration before I can start watching from my MS.
Look forward for the new release soon for the ARM NAS'.