Cheap turnkey Linux server software for networks?

[stefano_mbp]

Just a suggestion .... why not give a try to Minimserver/MinimStreamer?

You could install it on your Synology nas very easily and configure it (thanks to MinimStreamer) to upsample everything to the maximum PCM rate your dacs can accept. Unfortunately MinimStreamer cannot upsample to DSD but you could stream native DSD tracks anyway.
Beside Minimserver you could install Bubbleupnpserver on the same nas.

This will let you to use Lumin app as control point and stream to your Rendu renderers with MPD/DLNA enabled. Lumin app integrates with Minimserver wonderfully.
Bubbleupnpserver is needed to create OpenHome compatible devices of your Rendu devices, Lumin app needs OpenHome devices to work correctly.
With your music files well tagged this solution should work very well.
If your nas were not powerful enough you could install Ubuntu on your Nuc and then install there Minimserver/MinimStreamer with Bubbleupnpserver.

I use this last configuration (but with a NUC8i3) and I can stream to my SOtM sms200 Neo and I’m very satisfied 

[stefano_mbp]

8 minutes ago, bluesman said:

I'm 99% certain that JRiver will output files to networked DLNA devices upsampled to DSD

.... the 1% left wins .... I can confirm JRiver cannot upsample to DSD using DLNA.

It can play dsf files as native dsd or DoP and can upsample pcm but not dsd.

You can find the answer from JRiver support staff here

https://yabb.jriver.com/interact/index.php/topic,92801.msg867905.html#msg867905