The www/qt5-webengine port has the option to use alsa as sound backend. But the browser (www/falkon in my case) doesn't have sound when the alsa option is checked. After manually installing audio/alsa-utils (and audio/alsa-plugins as a dependency), sound does work. So I think the audio/alsa-utils port should also be installed as a dependency of the www/qt5-webengine port when the alsa option is checked. I should say that I also checked the ffmpeg option in all ports which may help too.
Since using sndio for all ports for some time now, closing this one.