Yeah multiview is complicated to implement as you need to update your shader to take care of the specific info that are required by the multiview extension.
First you need to add
#extension GL_OVR_multiview2 : require\nlayout (num_views = 2) in at the beginning of your shader
then you need to know that you will receive 2 viewProjection matrices like here:
What we do automatically for you is that if your defines contain “MULTIVIEW” we will add the extension declaration
then you need to test for #ifdef MULTIVIEW and add the shader code: