In my mind such a question should be treated similarly to questions asking for textbook recommendations. That is they can be on-topic, but only if asked carefully.
The key to making such a question work is making it specific regarding the math (yet not your personal circumstances). If you have some specific math-problems, or a class of problems, you want to solve and ask for software to do this, this can be a good questions.
Technical "limitations" can also be mentioned (hardware, OS, price, etc.)
[Yet I would try not to put too much emphasis on them. ]
By contrast, an overly general and vague question like "What CAS would you recommend for a graduate student interested in algebraic geometry?" is not good.
For the tags: the mathematical subject to which the problems you want to solve belong, math-software and possibly computer-algebra-systems