Looking for support or purchasing advice with Apple’s Home app, accessories, networking troubles / solutions, anything else HomeKit supports, or which brand or accessory to buy — try asking here.
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Here is a list of HomeKit enabled devices on Apple’s website.
When you have the remote on screen use the device volume rocker on the side of the device.
Right, but your TV has to support HDMI-CEC with volume change support
Only if you’re controlling via AppleTV. If you have a HomeKit TV it doesn’t require that AFAIK (though likely will have it).