PS: which standard app you had in mind?

Thank you for your fast reply. I will clarify it a bit more. Yes, I'm sure, I will need it, as I will support an ecosystem, as you said. The Matterwebsite points you to Mattersupport. I already created a small test app with nothing then a button to run MatterSupport in it's extension. I used the test app as host for the extension then, same like I did it for Siri or AppWidgets (should be the same flow for the Matterextension, or am I wrong). What I expected, is, that at least the init function will be triggered in the debugger, but even this isn't working. So I guess, I missed something adding the extension correctly.