Comment 8 for bug 1841746

Yes the lowlat kernel is optional. perhaps try removing ubuntustudio-performance-tweaks. I can think of nothing else that may be causing this.

Have you set up jack (using ubuntustudio-controls or Cadence) to autostart at session start? If so try turning jack off just before rebooting/shutting down. (not sure how to do that with Cadence)

It would appear that there is one package causing your problem. So far we don't know what. What with the move systemd, I am not sure where to look for log files that might show something useful.