Error Download and APT Package

[gianfelicevincenzo]

Hi. Report this error:

Err:21 https://packagecloud.io/JonasGroeger/soundnode/debian stretch Release
  404  Not Found
Lettura elenco dei pacchetti... Fatto
E: The repository 'https://packagecloud.io/JonasGroeger/soundnode/debian stretch Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

and this:

sudo apt install soundnode
Lettura elenco dei pacchetti... Fatto
Generazione albero delle dipendenze       
Lettura informazioni sullo stato... Fatto
E: Not Found soundnode

From Site(not found) https://packagecloud.io/JonasGroeger/soundnode/debian:

I'have Debian 9(Stretch)

[doctortee]

For debian, there's only a jessie repo. Edit your source.list file and replace "stretch" by "jessie" for soundnode repo (it works for me on debian testing / buster)