edge repository has sndio package but support isn't being enabled at build time in other packages
e.g. in the build log from the mplayer package also in edge community: "Checking for sndio audio ... no" "Enabled optional drivers: Audio output: alsa oss v4l2 sdl mpegpes(dvb)" "Disabled optional drivers: Audio output: sndio sun openal jack pulse nas esd arts ivtv dxr2"
The same for mpv in edge community: "Checking for sndio audio input/output : disabled" and vlc: "checking sndio.h usability... no checking sndio.h presence... no checking for sndio.h... no"
I am not sure whether the firefox package in edge testing has it enabled, but it would be really nice if it has because while I wouldn't mind compiling mplayer myself, compiling firefox every time a new version is released is not a possibility for me. Also, ALSA support (on which the Alpine package appears to rely currently) will be removed from the code base in the near future according to Mozilla developers, so it appears sndio will be the only way to avoid pulseaudio in Alpine then.