In the Raspberry Pi CEC automation I mentioned that my Samsung TV is on ARC (not eARC). This is the backstory: eARC wouldn’t stay put, so dropping back to ARC was the only reliable option.

Setup

Samsung S95B hangs on the wall, its eARC port feeds a Denon AVR-X1700H, and every source runs through the receiver with CEC enabled.

With HDMI eARC Mode = Auto, the S95B would sometimes boot to TV Speakers instead of “Receiver (HDMI-eARC),” silently fall back to TV Speakers after source changes, and after the 1651 firmware update it would wake up that way every single time even with an ARC/eARC device attached (Samsung Community).