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