This is one of the features I like in Learning Catalytics (from Pearson).
It's not free but it is relatively cheap ($12 / 6 months) and is not tied
to any LMS.
The "Expression" question format recognizes equivalent symbolic
expressions fairly well. There are just a few restrictions like having to
type sin(θ) instead of sin θ.
There is also a numeric question format where students have to enter units
(provided you put that in the set-up (something I can't do on Canvas, our
LMS). So both 0.5E-3 A and 0.5 mA are considered correct even if I coded
the response in only of these forms.
Almost a full semester later and my students still get caught doing the
calculations correctly but not putting the unit (or sometimes the wrong
unit) when they type in their answers.
Oddly enough this system does not have questions with randomized values.
I wonder if other LMS systems will also adopt this STACK system or
something similar. Canvas has a few things but the STACK list seems more
extensive.