How to reproduce:
1. Open the “ReproProject.zip“ project
2. In the “File > Build Settings“ switch to the iOS module
3. Build the Xcode project
4. Open the “Unity-iPhone.xcodeproj“ file in Xcode
5. Build to a physical device
6. Put the device to sleep and wake it or swipe up the application to enter App Switcher and select the app from one once again

Expected result: The application does not freeze
Actual result: The application freezes

Reproducible with: 2022.3.58f1, 6000.0.38f1, 6000.1.0b6, 6000.2.0a3

Reproducible environment: macOS 15.2 (M4 Max)
Not reproducible environment: No other environment tested

Reproducible with these devices:
VLNQA00535, iPhone XS (MT9F2ET/A), CPU: Apple A12 Bionic, GPU: Apple designed, OS: 17.6.1
VLNQA00416, iPhone 13 Pro (MLVA3ET/A), CPU: Apple A15 Bionic, GPU: Apple designed, OS: 16.1.1
VLNQA00626, iPhone 16 (MYE73QN/A), CPU: Apple A18 Pro, GPU: Apple designed, OS: 18.0.1
VLNQA00232, iPhone 8 Plus (MQ8M2ET/A), CPU: Apple A11 Bionic, GPU: Apple designed, OS: 16.7.10
VLNQA00600, iPad Pro (9.7 inch, WiFi), CPU: Apple A9X, GPU: Apple designed, OS: 14.8 (The application freezes on launch)

Notes:

Exchange the “UnityBatchPlayerLoop()“ to the “UnityPlayerLoop()“ in the “.mm“ files in the Xcode project, not a workaround “UnityPlayerLoop()“ causes a flood of OS errors since Unity (Metal) is trying to use the graphics while in the background
It freezes on the first launch of the app from Xcode, but consistent reproduction will happen once the app is put to the background and brought back to the foreground