Skeleton project has low FPS on some Android phones in landscape

Problem

Low FPS on Android, in landscape mode, on an almost empty project.

Problem reproduced on

1. Samsung SM-A530F (A8), Android 9

2. Samsung SM-A750F (A7), Android 10

   Problem NOT reproduced on

   1. Lenovo Tab2 A10-70F, Android 6.0

      How to reproduce

   2. Install IDE : Unity 2019.4.12f1, SDK Android 26

   3. Create an empty 2D project

   4. Add a text field in the middle of the screen

   5. Add script to text field

   6. Modify Update()

      1. Add code to display FPS on text field 2. Call that code about twice a second

   7. Modify Start(). (not mandatory - problem occurs with or w/o this code)

         Application.targetFrameRate = 60;
         QualitySettings.vSyncCount = 0;
      
      

   8. Compile and load to Android phone

   9. Rotate phone to portrait

   10. verify constant ~60FPS, almost never changes

   11. Rotate phone to Landscape

   12. verify ~60FPS initially

   13. Wait 5-10 seconds

   14. Observe FPS drop to 40-45 <== This is the problem