SUMMARY plasma-pa switched to using gsettings instead of gconf by default (https://phabricator.kde.org/D14147) Neon still ships PulseAudio with module-gconf, so plasma-pa needs to be build with -DUSE_GCONF=On to not loose advanced settings.
Even with -DUSE_GCONF=On it still errors with No package 'gconf-2.0' found https://build.neon.kde.org/job/bionic_unstable_kde_plasma-pa_bin_amd64/81/console Great that you tell neon but have you told the oher distros? We have a release-team@ mailing list and a distributions mailing list We use Pulseaudio 11 which indeed doesn't look like it has the gsettings module.
This is no longer relevant in focal-based neon