These need to be read-only. The way you've typed it, you're allowing a caller of getOwnPeerDevices to directly mutate the Redux state, which should never be possible. The Redux state should only change in response to actions being reduced

This function is named in a similar way to the one above (getForeignPeerDevices), but it returns something different.

1. Can you clarify why we need PlatformDetails here but not above?
2. In a separate diff, can you either update the naming to be more clear (ie. maybe rename getForeignPeerDevices to getForeignPeerDeviceIDs), or update getForeignPeerDevices to also return $ReadOnlyArray<DeviceIDAndPlatformDetails>?

I don't love this use of ternary and ??. I think this is more readable:

if (!currentUserID) {
  return [];
}
const devices = auxUserInfos[currentUserID]?.deviceList?.devices;
if (!devices) {
  return [];
}
return devices.map(deviceID => ({
  deviceID,
  platformDetails:
    auxUserInfos[currentUserID].devicesPlatformDetails?.[deviceID],
}));

It looks like this diff includes a move. In the future, please make sure you always separate code refactors like this into their own diffs. See here:

{F2381628}