Unity UI does not work with camera's custom projection matrix

Has anyone had the issue with using a custom camera projection matrix, which then prevents Unity's UI from showing on the screen?

I'm not sure if there is a good fix for this, outside of using a second camera to render the UI, which for my scen wouldn't be ideal as I already have 4 splitscreen cameras that would require and additional 4 cameras for each of the UI elements of each of the 4 viewports.

 

To have a custom camera proj matrix you have to use another camera for the UI using either a ScreenSpace - Camera or Worldspace canvas. As this is the only way to alter the Canvas projection.

 

You were able to solve this? Thanks!