VR camera shake for Vive Focus

Hi,
I'm trying to use a camera shake script inside my Vive Focus.
I've found this tutorial on how to create a VR camera shake that doesn't make people sick:
http://www.zulubo.com/gamedev/2019/1/5/vr-screen-shake-the-art-of-not-throwing-up

Sadly, this work inside the editor, while it doesn't work when deployed inside the Vive Focus.

Probably it's something related to the platform and how the shaders are executed, inside the guide there's only a tip on the shaders:
"Use Mobile simplifier shaders first, and avoid using “Standard” shader
There are several simplified shaders under “Mobile” category on Unity Mobile platform. These shaders can provide significant performance advantage. For example, some shaders support only one directional light and not support alphaTest or ColorMask."

I am not an expert, and perhaps here I will find someone who can point me to the right direction...any advice, link, keyword, suggestion and experiment is welcome, I have no clue on where to start modifying it to make it work.

Thank you in advance
Francesco