What you can do is create a new camera and use it for the hud. Set it to depth only and make the depth the highest of all camera’s. Make sure the near clipping is lower than the plane clipping distance of the canvas or parts of the hud won’t show. Set the hud ui to a unique layer and set the culling mask of the camera to that layer. This all will prevent the hud from getting hidden by other objects.
Attach the camera to some view that you control so that you won’t have lag.