macOS: Surround Monitoring, USB Hardware Solutions?

Using Premiere (and Audition) CC 2018 on macOS High Sierra 10.13.2 (Mac Pro 5,1 and MacBook Pro).  Curious what current hardware solutions people are using to monitor and mix surround and multi-channel audio?  Looking for USB 2 or USB 3 solutions (not Thunderbolt) that would allow mapping to each speaker for 5.1 or 7.1 setups.  Searching through forums and only finding old posts referencing fairly outdated and unavailable hardware.  Unfortunately, HDMI embedded audio out solutions will not work and would like to avoid Toslink S/PDIF through a receiver.