Officially Plugable USB 2.0 Gigabit Ethernet Adapter is only compatible with computers running Windows, Linux, or macOS/OS X, and some Android devices.
Typically USB ports on home theater and home audio equipment are for accessing audio files that are on some form of USB storage, rather than adding functionality like Ethernet, Bluetooth, or Wi-Fi.
In this case, the manual for the McIntosh MB50 streamer indicates:
When connecting the MB50 to a wired Home Computer Network (of which includes a wireless router) a USB (2.0) to Ethernet (RJ45) Adapter such as a Monoprice (109466) is required.
The “Monoprice (109466)” Ethernet adapter has an ASIX AX88178 chipset, which is the same as the one that is used in our network adapter (Plugable USB2-E1000).
Given McIntosh’s documentation, I would say that our adapter would work in this case.
I hope this helps!