I've switched from RecalBox to a new RetroPie build, and recording is working again with audio.

The audio driver in RetroArch is set to alsathread (not pulse).
When I tried alsathread in RecalBox I got no sound, i only tried this once though.

The solution for this issue on RecalBox may be to switch from pulse to alsa or alsathread as the audio driver.

I recently installed 9.1-Pulstar on a Raspberry Pi 4, all is working well expect for missing audio when recording in RetroArch.

I have tried many combinations of audio drivers, audio filter, custom configuration, and a vanilla rebuild without managing to solve this issue.
Audio in game works fine, video recording is also working except for the missing/silent audio (the audio stream appears to be present just no sound).

Previously I had been using RetroPie on the same hardware and had no issue recording with sound in RetroArch (although I think I had disabled pulse and was using alsa for audio due to a separate issues),

Is it possible to record with audio using the current 9.1-Pulstar on Raspberry Pi 4 - or is there a known issue with this?

I would love some help from anyone who has successfully recorded audio on a Rpi4 this as this is a showstopper for my Recalbox cabinet build.

Potentially related open issues here:
https://github.com/libretro/RetroArch/issues/13580
https://github.com/libretro/RetroArch/issues/13021
https://github.com/libretro/RetroArch/issues/11667