@juas I have recently changed over from RetroPie to Recalbox and I'm experiencing the same issue with Recalbox 9.2.2-pulsar. I'm using the same Raspberry Pi 3b+ connected via HDMI cable to my TV. The sound bar is also connected via HDMI cable.

I tried adding the following line to the /boot/recalbox-user-config.txt file but this didn't help:

hdmi_ignore_cec=1