Usually you actually need to not use third party apps. RCS on Android is usually restricted to Google Messages (or maybe Samsungs built in messages app). Everyone else got the boot
You also sometimes have to enable in the settings for Android Messages (and have a supported carrier). iMessage also has an option to enable RCS but I believe its on by default in the newer versions of iOS
You also sometimes have to enable in the settings for Android Messages (and have a supported carrier). iMessage also has an option to enable RCS but I believe its on by default in the newer versions of iOS