O problema estava em system.pa. Eu encontrei no manual que na configuração do daemon do sistema inteiro não deve usar a detecção automática.
das páginas de manual do pulseaudio:
--disallow-module-loading[=BOOL]
Disallow module loading after startup. This is a security feature since it disallows additional module loading during runtime and on user request. It is highly recommended when --system is used (see above). Note however, that this breaks certain fea‐
tures like automatic module loading on hot plug.
Então eu desativei linhas (comentado) de system.pa
### Automatically load driver modules depending on the hardware available
#.ifexists module-udev-detect.so
#load-module module-udev-detect
#.else
#### Use the static hardware detection module (for systems that lack udev/hal support)
#load-module module-detect
#.endif
e agora funciona.