I’m unsure what you mean by gated free speech zones. Sometimes specific areas are closed to vehicle traffic for a protest, but that doesn’t mean those locations are exclusively for protesting. In general protest is allowed wherever, provided it’s not on private property.

There are occasionally attempts to keep protestors away from wahtever's being protested. They tend to not do well when challenged in court.

Here's a couple (opinionated, obviously) articles:

https://www.fire.org/research-learn/free-speech-zones

https://firstamendment.mtsu.edu/article/free-speech-zones/