As much as mediation or legal action are things to keep in mind as options for age discrimination at the university level, it is as well to remember that much of the concerning behavior experienced may not originate from the institution itself, but from other members of the university community--which one cannot realistically control with litigation (certainly not without incurring other unintended consequences). In any case, my experience with early entrance/radical acceleration with university students as young as nine has been that not nearly as much age-based discriminatory behavior occurs as one might fear. The more important questions typically are within-student, and focus on social maturity and executive functions, some of which can be scaffolded by thoughtful adults around the student.
For our children, we took advantage of relatively generous access to dual enrollment classes (especially online), as a reasonable compromise between full in-person university enrollment as a matriculated student and adolescent (or younger)-level social/EF skills. I would also agree that AP exams are a viable option both for accumulating college credit and for scheduling more challenging course syllabi in your homeschool instruction. We have also used them.
The child I mentioned upthread was multiply grade-advanced, but then requested a one-year retention back to grade 11 as we were preparing to enter grade 12, because they felt they were not ready for college--but then of course, ended up with a full schedule of dual enrollment classes, entering university as a sophomore the following year--putting them in the same position in the end. My point in this latter anecdote is that flexibility is key, and careful attention to the bursts of development that any children--but especially GT kiddos--tend to have. Make plans, but be prepared to change them, and don't let your anxieties run too far ahead of reality.
