Robad, sorry for the tardy response.
I ran into world of trouble trying to achieve much the same as you, here is what I found (MC ver 21.0.93) :
- MC for QNAP is very sluggish, unstable and cannot be relied upon. It will crash or freeze even when "doing nothing".
- MC for QNAP is, as you point out, rather limited it its libary management capabilities and will fail at certain tasks.
- MC for QNAP apparently caused corruption in the libary, and Playlists stop working (appears to lose the location of the file, even though nothing has changed)
- It is not clear to me where MC for QNAP stores its libary files, they are not readily accessible from the NAS (I asked the question in the QNAP forum, but no one knows apparently). At one stage MC showed my libary as having grown from 23MB to over 400MB, but couldn't find out how to access the libary files on the QNAP to see what was going on, so had uninstall and try again.
I suspect that the different path syntax between Windows and Linux is causing much of the grief and library corruption and makes it hard to migrate a library from a MC Windows to MC QNAP. I've tried many ways and the only way that had some success with was to open the existing Windows library in QNAP then clone it and do a file path replacement on that clone. That worked for a while before the library became corrupted again such that MC wouldn't even start.
So my current situation is that I have abandomed MC for QNAP for now, it simply doesn't do the job reliably or anywhere near as well as the Windows version. My current set up is:
All media files nd libary reside on the QNAP NAS and I leave a PC running 24x7 with MC 21 just to serve MC Clients on various other PCs and Gizmo on Android. Using MC for QNAP as a client for this libary will work sometimes, but it is very slow and unstable and will crash after a while, so now I use Kodi and Plex when I'm playing media files on the QNAP (connected to receiver and TV) and they are stable and work very well, albeit without the MC functionality and library management I would like. (Note. syncing the libary on QNAP with Windows MC Server causes library corruption too).
I had hoped to use the QNAP NAS as the main engine to lower my power usage, but alas that is not possible at the current stage of development. I may revisit this if J River choose to release a MC22 version for QNAP, but otherwise I'll stay clear of Linux and the incompatibilities that are apparent with Windows clients.