Unable to use ALSA JACK PCM plugin on Debian 10 and on raspbian

[GitHub issues - opened]

alsa-project/alsa-plugins issue #15 was opened from UgoPoddine:

Hello everyone,

a) I have installed libasound2-plugins from repository on a Debian Buster machine (4.19.0-12-rt-amd64 #1 SMP PREEMPT RT Debian 4.19.152-1 (2020-10-18) x86_64 GNU/Linux)  and on a raspberry PI3 (5.4.79-v7+ #1373 SMP Mon Nov 23 13:22:33 GMT 2020 armv7l GNU/Linux) up-to-date (none of these running  pulseaudio of course)
b) I have modified  my .asoundrc configuration file according to https://jackaudio.org/faq/routing_alsa.html
c) I can see jack and rowjack virtual devices in aplay -L
d) starting qjackctl I'm unable to see the expected new capture_x devices. Of course jack runs correctly with physical devices (eg. PC mic or USB mic)
e) jack is at jackd 0.125.0rc1 version
f) Alsa is at Version k4.19.0-12-rt-amd64 on the AMD64 machine, at Version k5.4.79-v7+ on the RaspberriPI machine
e) any attempt of playing test files over jack device (aplay -D pcm.jack <wav file> ) generates the error :

ALSA lib pcm_plug.c:1286:(_snd_pcm_plug_open) Unknown field playback_ports
aplay: main:828: audio open error: Invalid argument

Can you help ?

Thank-you
Best regards
Ugo Poddine

Issue URL     : https://github.com/alsa-project/alsa-plugins/issues/15
Repository URL: https://github.com/alsa-project/alsa-plugins