Cardboard is still here, YouTube app can play VR videos via it, Chrome for Android provides WebXR support via it, it's 3DoF only, but main usecase for phone VR is VR stereoscopic video which is 3DoF anyway. Daydream was attempt to create another proprietary ecosystem and is obsolete. Since then OpenXR has won as cross platform, cross vendor, open standard XR API, if Android gets standard OpenXR runtime with good 6DoF tracking and shell support everyone will be happy.