I have been having the same issue on iPad Pro 2017 9.7inch with the latest iOS and updated Minecraft. Upon start up, the screen will freeze on loading half way through to 3/4 the way through and will not proceed.
Most of the time I am unable to load the game. About 10% of the time, the game will load to the character screen but then will freeze.
I am also unable to connect to realms on multiple devices.
iPad and Windows 10 computer.
It has been down for over 12 hours now.
The day before, realms was not able to load for a number of hours as well.