https://bugs.freedesktop.org/show_bug.cgi?id=104880
--- Comment #8 from Konstantin A. Lepikhov lakostis@altlinux.org --- Sound is back when I've switched monitor via HDMI:
$ cat /proc/asound/HDMI/eld#0.4 monitor_present 1 eld_valid 1 monitor_name ASUS PB278 connection_type HDMI eld_version [0x2] CEA-861D or below edid_version [0x0] no CEA EDID Timing Extension block present manufacture_id 0x6904 product_id 0x27a3 port_id 0xd9894495558859e support_hdcp 0 support_ai 0 audio_sync_delay 0 speakers [0x1] FL/FR sad_count 1 sad0_coding_type [0x1] LPCM sad0_channels 1 sad0_rates [0x4e0] 32000 44100 48000 96000 sad0_bits [0xe0000] 16 20 24