Some time ago I started a topic "No Dolby Digital if HDMI-CEC is on (PCM still works) - QN95A"

https://eu.community.samsung.com/t5/tv/no-dolby-digital-if-hdmi-cec-is-on-pcm-still-works-qn95a/td-p...

Now, exactly the same problem exists with S90C firmware 1410 and Yamaha RX-V473 receiver.

When HDMI-CEC is enabled in TV settings, only PCM audio signal is recognized by receiver.

When HDMI-CEC is disabled in TV settings, then Dolby Digital or DD+ are recognized by receiver via optical cable (there is no option in TV to send audio signal via HDMI in this scenario).

Just to add, HDMI-eARC option is disabled in TV settings as my receiver supports HDMI-ARC only.

Based on the comments from the previous topic, I understand that TV firmware update solved the problem - now it seems we need to request Samsung to look at their code repository and apply the same fix again.