The majority of receivers above a certain point have streaming radio, "cast", and/or "smart TV" features. Just like so much of the rest of the appliance world, most of those are powered by some random ARM or MIPS SoC running some flavor of Linux.

A modern networked AV receiver is sort of analogous to a managed switch, there's a fairly generic CPU running a general purpose OS presenting the user-facing interfaces, managing configuration, and handling some housekeeping tasks, then there's specialized hardware that actually deals with the signals and does the real heavy lifting after being set up by the general purpose processor..

Emotiva XMC-1