Buzztrax consists of a few modules with separate issue trackers. You’ll need a (free) github account to file tickets. If not sure file them for the main module: ‘buzztrax’.
buzztrax: the main module, includes the UI
gst-buzztrax: extra GStreamer audio plugins
bml: the buzzmachine loader, for issues with buzzmachine plugins
buzzmachines: the open source buzzmachine archive
Feel free to submit ideas as well. When filing bugs please include details as the version of the application/libraries you are using (or the git version if you built yourself) and what platform you are on (linux distribution or e.g. macos). Feel free to attach screenshots or debug output logs.