From this thread, my understanding is that QTS 4.2.0 is required for optimal Sooloos functionality.

The caveat is that QNAP have withdrawn access to v4.2.0. So, if you buy a new QNAP device, with the latest QTS firmware, you cannot utilise v4.2.0.

On that basis, it's pointless buying the latest QNAP as part of an integrated Sooloos system.

Not an Actor, nor married to Jamie-Lee Curtis.

#1: DSP5200SE|DSW.2|218|210|506.2|504
#2: Prime/PSU|SOtM sMS-200 Mini NEO SE|Focal Stellia
#3: Other stuff