I'm using KXStudio. Cadence starts automatically at login. It used to start JACK automatically, but now it doesn't. I can start JACK (according to Cadence) either from Cadence itself, or by booting the server in SuperCollider. Whenever I start JACK I get a popup notice, "Automatic studio created: JACK server is started not by ladish daemon and there is no loaded studio, so a new studio is created and marked as started."
With JACK running, I can use SuperCollider as normal, but no other apps. It used to be that with JACK running I would see it in the KDE toolbar, but now that's not true.
If I open a Youtube video in Chrome, I get video but no sound. If I play a SoundCloud clip, the view advances as if playing but no sound. In Firefox, SoundCloud won't even start; I only get a circular icon that spins forever as if it's about to start. In VLC, if I open an mp3 file, I get
Audio output failed:
The audio device "default" could not be used:
With JACK not running, if I "force restart" in Cadence, I get a a popup report that ladish daemon has been deactivated. With JACK running, if I "force restart" in Cadence, I get popup reports that ladish daemon and jackdbus both crashed.
I've rebooted a lot.