It's quite possible I am doing something wrong or missing something here but when building an image with IMAGE_INSTALL += "pipewire pipewire-alsa" the configuration files (50-pipewire.conf and 99-pipewire-default.conf) are installed to /usr/share/alsa.conf.d/ but my understanding is that they need to be symbolically linked from /etc/alsa/conf.d to be enabled.