Matrix Voice on Raspian/Debian Bullseye?

Hi
Are there experiences in running a Matrix Voice on Raspian/Debian Bullseye?
Normal installation fails:

...
Reading package lists... Done
E: The repository 'https://apt.matrix.one/raspbian bullseye 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.
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package matrixio-kernel-modules

I was able to build the drivers as suggested in this post but the Matrix Voice is not recognized:

$ aplay -l
aplay: device_list:274: no soundcards found...