Homekit volume control of Roku TV broken when soundbar connected
I have several Roku TVs and they work fine in homekit since the 9.4 update added this feature. However, I recently connected a soundbar to one of my TVs (Sonos Beam) via HDMI-ARC and noticed that now I can no longer control volume over HomeKit anymore. When I use volume controls on the Apple control centre remote, the current volume level is displayed on the TV but will not change. If I disconnect the soundbar, I can control the TV volume.
It seems this is a bug and the volume change command is not being sent over HDMI-ARC.