1. Open a project on a mac and change to IOS preview mode.
2. Select an actor.
It will output a lot of logs as Time out while waiting for GPU to catch up. (500ms).
It will be ok after disabling Occlusion Culling.
The 4.21 does not have this issue.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-76875 in the post.