The officially supported way to get sound on Chimera is through the PipeWire project. Plain ALSA is not supported. PulseAudio is also not supported (but PipeWire provides compatibility).
In longer term, other sound servers may become options, but PipeWire will remain a well supported default.
PipeWire
To install PipeWire:
# apk add pipewire
This will also automatically install WirePlumber, the default session manager.
The primary supported way to get the daemon running is through a user service. Simply enable WirePlumber as your user:
$ dinitctl enable wireplumber
Doing so also implicitly enables pipewire
itself. Typically
you will also want PulseAudio compatibility:
$ dinitctl enable pipewire-pulse
You can check whether it’s running:
$ dinitctl list
[[+] ] boot
[{+} ] system
[{+} ] dbus (pid: 1040)
[{+} ] pipewire-pulse (pid: 1046)
[{+} ] pipewire (pid: 1044)
[{+} ] wireplumber (pid: 1045)