I have installed Nextcloud on https://Domain.tld and piwik is running on https://piwik.domain.tld. I try to configure piwik for tracking User, Visits and public Downloads. I read many howtos but only for Owncloud.
I Insert the Java tracking Code in the body section from /core/templates/layout.user.php
/core/templates/layout.guest.php
If you’re referring to how the app behaves on your installation, the best thing to do is to contact the developer using the tracker which has been defined.