If you go to Special:Gather/all/public and there are no collections, a totally empty table is shown. This could be used as a CTA to create a collection, like the Android app does for saved pages and history.
This also happens on the new Special:Gather public feed introduced in T101115
Practically this will never be empty unless it's a totally new wiki. Given that this is (right now) being developed explicitly for Wikipedia which makes it actually impossible (practically speaking) to ever get into this state, I am marking this as lowest priority.
We're also not sure about the future of this page but yeah at some point we'll want to look at this.
This task was declined as part of a batch-decline related to sunsetting the Gather project. Please ping (politely) if this task should be reopened. For more information, you can also see here: https://www.mediawiki.org/wiki/Extension:Gather