As recently as 18 months ago or so, I had my ancient Airplay Express operating as an airplay destination without a hitch. Apple had updated it with Airplay 2. But when I went to reconnect it after a long hiatus and put it on a new router, I couldn't get it to connect to HomeKit, though I was able to do my other third-party speakers that likewise lack homekit codes. Worse still, when I airplayed to it, it grabbed VO's speech. When I managed to get audio destination back to default, the VO volume kept spiking up and down with each swipe. Tried this a few times. No such behavior on my other airplay receivers.
So I guess AE is just ready for the graveyard, unless I wanted to use AirFoil? Let me know if anyone else is having better luck.
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Apple Hardware and Compatible Accessories