Hi
We managed it for our app without detaching.
Expo will let you get the device token from GCM and APNS. Have a look at this
https://docs.expo.io/versions/v27.0.0/sdk/notifications
Expo.Notifications.getDevicePushTokenAsync
Once you’ve got the token, you will obviously need to send it to whatever PN server solution you’re going to use. This will be the hardest part.
We had some gotchas in the formatting of the json message that gets delivered to the device, but expo was able to serve it to the users phone on both android and iOS and open the app up.
Also, obviously you will not retrieve a token via an emulator or a published expo app via the client. It’s got to be a published APK or an IPA.
Read the bottom of this for an idea of the format, but expo have said this may change in later sdks https://docs.expo.io/versions/latest/guides/push-notifications
Also, we are on SDK 24. I know there’s been some changes with FCM but docs indicate it should be the same.