On my iPhone 13 Pro Max, I cannot find OPRA. It does not appear when touching Headphone EQ (whether turned on or off) and there is no + sign to add filters, such as OPRA.
Your MUSE (DSP) configuration above shows ‘Headphone EQ’ disabled. This is the filter associated with OPRA.
This is what will happen by default if you look at the MUSE configuration of an endpoint that has not been modified since OPRA was introduced. However, you cannot configure headphone EQ on a phone.
On phones (both Android and iPhone), you can not configure all of the MUSE (DSP) options. Many configuration options have to be configured using a Windows or Mac client or using a tablet (Android or iPad). The configuration options that are not available on phones include (but are not limited to) adding new filters (e.g. The Headphone EQ headphone selection in Headphone EQ and even adding Headphone EQ if it is not already present).