PeteB
It seems your doubts about MiniDNLA's compatibility with RuneAudio may be well-founded!
I conducted the experiment you suggested, twice. The first time I copied-across, unaltered, the directory <Instrumental> (complete with its sub-directories) into the new share "testshare" . It failed - with the error-message "mount.nfs: access denied by server while mounting 192.168.11.5:/testshare/Instrumental/Bach keyboard".
To be doubly sure I then tried putting the actual music file (NB: in .flac file-format) I was trying to play directly into "testshare" without any sub-directory/ies - just in case it was those that Rune was objecting to. This only resulted in the same error-message, but minus "/Instrumental/Bach keyboard"
Unless it is the file-format which is the problem, therefore, it appears that MiniDNLA may be a no-no for Rune - alas!
Unfortunately none of the other media servers my NAS's firmware provides meet my needs, for various reasons, whereas MiniDNLA seemed the ideal choice. Ah well....
Any alternative ideas would be welcome. Meanwhile many thanks for your interest and help.