Mojang has announced end of support for certain older devices and platforms effective in October 2020.
Effective in October 2020, Minecraft will no longer be updated or supported on Gear VR, Windows 10 Mobile, Android devices with less than 768MB of RAM, iOS devices running iOS 10 or below, or video cards that only support DirectX 10.1 or below.Minecraft
For anyone playing Minecraft on Gear VR and Windows 10 Mobile, this move will prevent them from using multiplayer or Realms.
However, players on affected Android or iOS devices with a Realms subscription, will be able to continue enjoy their Realm until they choose to update it on a different device. (Multiplayer will only work between devices on the same version.)
If you would like to move your worlds from this device to another device, you can do so by uploading the world to a Realm, and downloading a backup onto your new device. Or you can transfer your world files off the device directly by following these instructions.Minecraft
More information on the topic can be found on this page