I’m not sure if ReactVR is still under development.
Using ReactVR with THETA Images
Most people are using A-Frame for VR applications.
This is an example with Electron
HowTo: Develop 360 Image Desktop Apps with JavaScript and RICOH THETA
There’s some information on Cordova here:
Building Cordova Apps for RICOH THETA 360 Images
There is currently no example for Expo.
Most people use these examples:
GitHub - ricohapi/theta-api2.1-ios-sdk: RICOH THETA API v2.1 SDK for iOS
GitHub - ricohapi/theta-api2.1-android-sdk: RICOH THETA API v2.1 SDK for Android
You can also use Flutter. This tutorial series will take you through each step.