Strange problem, after he instituted a mandatory build for arm64, the size of the game has increased in 2 times, and also had problems. In Unity editor everything is fine on the Terrain textures on the ground are displayed correctly, after compile and run on the ipad 4, the earth is painted in pink, the texture on it. How to solve not know, did texture and with compression and without, nothing helps. On the Terran two 512x512 texture Wrap Mode Repeat.
If something is pink that usually means a shader issue. Are you using a custom shader for the terrain?
Are you seeing any errors in your log when launching the game from Xcode?