What is the minimum clearance (distance) between a trace and Ground with respect
to the DC voltage of that trace and the Ground?
Is there a table or some “rule of thumb” available?
Is my question THAT difficult?
It does not seem ‘simple’ to me. I do not have an answer. I can say that it probably varies depending on other factors. DC voltage is not the only consideration. If all you care about is whether is going to ‘short’, do the math using dielectric constants, and how ‘exact’ the trace edges are. A perfectly smooth edge will be better than one with small defects, but that is controlled by the specific manufacturing used. To me a ‘proper’ answer would need more information. Even with that, I could not answer from my personal background. Maybe there is a simplified rule, but I am not aware of it. At the voltages I work with, the manufacturablity of the trace size is more of a constraint than worrying about pushing the traces as close together as possible.