It isn't going to be an issue at most places.
My trick for checking what my options are: If you use mobile ordering, you can pick from whatever side options come up with the entree (for example at CHH the side choices are hushpuppies, carrots and green beans, apple slices, fries, house-made potato chips, and vegetable rice and at Cosmic Ray's I can select from fries or carrots- last month was green beans). A good way to see what's offered without having to ask is to check there first. If you know somewhere has a side that doesn't come up as an option on mobile ordering (like grapes or apple slices that come with a kids meal), it's worth ordering at the counter and asking for the substitute, most places are happy to do this.