You have different questions / answers due to being different hearing aids.
Ok so with Phonak, it’s completely different from your first post.
Phonak is not MFi so is not under Accessibility.
To mute Phonak when listening to audio / music, it’s a long press on bottom button but it needs to be activated in the Target Software.
It can also be set up for Mics to always be off. Note, not for Phone Calls.
Phonak for Phone Calls, you can’t mute, only option is to raise volume and that’ll lower the background noise.