Comment 3 for bug 1816278

With regards to lubuntu-desktop, we expect that metapackage to provide a particular experience and that includes a user-friendly sound mixer. We also expect it to include a terminal emulator. Xubuntu does things a little bit different: both the sound mixer and the terminal emulator (as a corollary; there are other examples) are recommends.

The solution: install the basic components or simply uninstall pavucontrol-qt. It will remove lubuntu-desktop but that's just a metafile. It won't remove your entire installation.