A while back, I started noticing that any program started from yakuake that plays audio was showing up as "yakuake" in Pulseaudio monitoring programs, e.g. pavucontrol and kmix. This didn't affect programs started from the desktop or krunner. Since upgrading to Plasma 5.18.0, all programs on my system started using any method show up as either krunner or yakuake. I'm not entirely sure where to begin debugging this.
Same root cause as Bug 417457, and it will be fixed once that's fixed, by the greater use of cgroups, which is planned fairly soon! *** This bug has been marked as a duplicate of bug 417457 ***