[Unity 5] Why is the Camera Clear taking so long on device?

This is problem on my main project, but I created a simple test case from a blank project. There are 2 active objects in the scene: camera and a sprite. On device (htc desire), using the profiler, the following line (Camera.Render-Drawing-Render.OpaqueGeometry-RenderForwardOpaque.Render-Clear) takes 12ms, which represent 33% of the time spend in the frame.

On the main project, it is the same story, except there are 4 cameras, so 4 x 12ms per frame are spend in "Clear". Other posters on the forum have reported that it used to work fine on 4.6 - something I have seen as well.

To Unity support: What does the "Clear" do exactly? Why is it so long? How to minimize the impact? Is it a bug?

To those who have shipped a game on android with U5: how did you deal with it?

Test device: HTC Desire, android 2.3.7. GRU: Adreno 200.
Test project: uploaded at https://dl.dropboxusercontent.com/u/27068517/CanvasClear.zip
Unity v5.1.1p4
Quality Settings: Fastest (tried adding VSync as recommender by 'bitter' in another thread, but no change)
Player Settings: Forward render
Camera setting: Orthographic, Clear Flags: Solid Color (tested with Depth Only as well - same result).
Shader: Default shader

Screenshot of the project


Profiler Screenshot of the "Clear" times:

 

I have the same problem on my android projects with a BQ Elcano 2 (ARM Cortex A7 quad core, gpu PowerVR SGX544)

 

I am having this same issue with Unity 2018.2 on a Samsung Galaxy S6. Were you able to figure out whats going on here?