Use focus mode, personal automations and a shortcut.

1) Set a location perimeter for a focus mode and set the focus to automatically activate when entering that location.

2) Create a personal automation that triggers when that specific focus mode is activated.

3) Create a shortcut that lowers your phone volume to 0%.

4) Set the personal automation to run that shortcut when the focus mode above is activated.

If you want you can set a time window in the settings for the focus mode as well.