Looks like the sound issue isn't related to Diaspora since OpenAL can't recognize any playback device. It may be my local problem:
$ openal-info
Available playback devices:
!!! none !!!
Available capture devices:
OSS Default
Default playback device:
Default capture device: OSS Default
ALC version: 1.1
** Info for device "OSS Default" **
ALC version: 1.1
ALC extensions:
ALC_ENUMERATE_ALL_EXT, ALC_ENUMERATION_EXT, ALC_EXT_CAPTURE,
ALC_EXT_DEDICATED, ALC_EXT_disconnect, ALC_EXT_EFX,
ALC_EXT_thread_local_context, ALC_SOFT_loopback
OpenAL vendor string: OpenAL Community
OpenAL renderer string: OpenAL Soft
OpenAL version string: 1.1 ALSOFT 1.14
OpenAL extensions:
AL_EXT_ALAW, AL_EXT_DOUBLE, AL_EXT_EXPONENT_DISTANCE, AL_EXT_FLOAT32,
AL_EXT_IMA4, AL_EXT_LINEAR_DISTANCE, AL_EXT_MCFORMATS, AL_EXT_MULAW,
AL_EXT_MULAW_MCFORMATS, AL_EXT_OFFSET, AL_EXT_source_distance_model,
AL_LOKI_quadriphonic, AL_SOFT_buffer_samples, AL_SOFT_buffer_sub_data,
AL_SOFTX_deferred_updates, AL_SOFT_direct_channels, AL_SOFT_loop_points
EFX version: 1.0
Max auxiliary sends: 4
Supported filters:
Low-pass
Supported effects:
EAX Reverb, Reverb, Echo, Ring Modulator, Dedicated Dialog, Dedicated LFE