Add a light path node then plug - is camera ray - into the Alpha socket of the principled node… It appears to significantly speed up the render and clear the glass up especially if it’s a bit dark or not enough light is getting inside of it to bounce around. Im not sure what its actually doing mathematically but it appears to be simplifying the glass shading but not resulting in anything too unrealistic.
It messes up the IOR.
Right. still useful tho if artistically it looks ok, compare the render times.