Can I use Siri to control the volume with my Sony bravia tv hands free

It will for sure if this is connected to Apple TV with either voice command or by ATV remote Siri button. As to no Apple TV I’m not sure, I just asked it but it couldn’t , but it could just be having a a temporary issue, it’s not something I ever used. I can ask Siri to turn the tv on or off. I added it to the Home App to facilitate this.

it's unclear if you mean using the siri remote or using siri voice commands

personally the remote always worked out of the box for me both with my sony bravia (old 40") and my current LG (where it's really a sonos soundbar that the remote inc and dec the volume on)