Schools can provide Alston benefits to all student-athletes, whether on scholarship or not. That amount can be up to $5980 per student-athlete per year. These awards are usually tied to academics/graduation, with each school able to set their own parameters.
Schools can provide meals and snacks at any time. While this isn't supposed to replace the meal portion of a traditional scholarship, schools can definitely fill in the gap of meals missed due to practice/games/other required activities.
Then there's always money in the NIL banana stand. Schools aren't supposed to dictate who gets money from their collectives, but I'm guessing walk-ons are getting some love there where necessary.
It's not a ton of money or benefits (especially at a school that costs $75k/year), but it helps.
A school that is over the scholarship limit will be able to offer access to an NIL deal that is considerably more than the cost of taking a few courses for a semester before the player declares for the draft.