Seeing as symbolic math tools are very common nowadays, how acceptable is it to skip calculations in manuscripts?
It's always been normal not to write out long but straightforward calculations in a scientific paper. If there are certain intermediate steps in the calculation that are of interest for their own sake, show them.


  will it be frowned upon, even if I specify which software I use and even provide code?


If the calculation is something that can be straightforwardly (but tediously) verified by anyone with knowledge of the field, then I don't see any point in saying what software you used or supplying source code. The reason to give this type of information would be if there was something in the software that could be nontrivial, controversial, etc., so that other people with knowledge of the state of the art might not get the same answer you did.