Nobody claimed my 3400X, so on a lark I plugged it into my Yamaha AV Receiver (RX-A740), which has an MHL-enabled HDMI port on the faceplate. Much to my surprise, not only did the Roku fire up, but the Yamaha remote works the 3400X, which otherwise couldn't be controlled since I removed it from my orphaned "RCA" TV. Regular HDMI ports see the stick, but can't control it.
So my circa 2012 Roku can be used by circa my 2014 receiver. No Peacock or Apple TV, but all my other needs are met. Glad I didn't toss it!