Hi, what you're describing sounds to me like a kernel issue, rather than an issue with the graphical environment. When you're comparing the bookworm/trixie behaviour on your HW, the bookworm->trixie upgrade (or reinstall) involves both the kernel and the graphical environment, then have you performed any further test to rule out any other possible software to be at fault but Plasma?
It could help in troubleshooting when you could check the behaviour with different graphical environments, e.g. GNOME, XFCE, LXQt... a live system could help you with this test [1]. It would help also to check whether the issue persists on old/new Plasma/kernel combination, but that's definitely going to be harder, then let's check whether the issue is specific to Plasma or generic to all graphical environments. Additionally, it would help to have the relevant journal log in this bug report: in order to capture that, please execute "sudo journalctl -f" in a terminal emulator, then perform the relevant steps (plug headphones, play audio in the "broken" state, adjust volume, play audio in the "working" state) and close the journal capture with Ctrl+C. Kind regards Marco [1]https://cdimage.debian.org/debian-cd/current-live/amd64/iso-hybrid/
