I’m running ardour 5.12 without Jack in ALSA mode. When I load my project I can specify my sound card under “Output device” and there is a button to start ALSA. The sound is on my headphones then, I wonder how to get it to HDMI instead. I can set the ALSA card but not the ALSA device.
You have an unusual hardware configuration, in that the HDMI outputs are a subdevice of your builtin audio interface, rather than a separate device entirely.
There’s no trivial way to specify this subdevice using Ardour. You can do it in JACK.
Ardour enumerates all the devices it finds, but not all the subdevices. Note the difference in the output on (e.g.) my system:
Odd, would be nice to investigate this, preferably interactively on IRC though.
Meanwhile you could try to start Ardour after setting an environment variable:
ARDOUR_ALSA_DEVICE=hw:1,7 Ardour5
That skips device-scanning and and, in this case lists 01-07: HDMI 1 : HDMI 1 : playback 1 as sole available device. It was added mainly as work-around for some rare edge-case where you need an explicit subdevice. By default Ardour5/ALSA always pick the first