The example ~/.asoundrc config file results in the error reported at alsa-project/alsa-plugins#15
ALSA lib pcm_plug.c:1286:(_snd_pcm_plug_open) Unknown field playback_ports
aplay: main:828: audio open error: Invalid argument
It seems that since that example was written, alsa-plugins now creates a default config at /etc/alsa/conf.d/50-jack.conf which is incompatible with the example. The simple fix might be to rename the pcm.jack device to something which doesn't conflict with 50-jack.conf.
The example ~/.asoundrc config file results in the error reported at alsa-project/alsa-plugins#15
ALSA lib pcm_plug.c:1286:(_snd_pcm_plug_open) Unknown field playback_ports
aplay: main:828: audio open error: Invalid argument
It seems that since that example was written, alsa-plugins now creates a default config at /etc/alsa/conf.d/50-jack.conf which is incompatible with the example. The simple fix might be to rename the pcm.jack device to something which doesn't conflict with 50-jack.conf.