1
There are two solutions.
The first would be to remove the Calc() of the LESS file, and placing it directly in the output CSS or even inline in the respective HTML file. This however generates a great discomfort without talking that seems a bit gambiarra.
The second solution was that after much research I found a code escape which the CPU itself makes available so that accounts are not executed. It works like this: you pass ~"" and inside the quotes go the operator that should not be compiled.
Example:
height: -webkit-calc(100vh ~"-" 6em);
Upshot:
The operation is not compiled by LESS and calculated in the browser.
Now yes, working in the right way.