Here's the scenario:
Ok...this is bonkers. Hub seems to hold on to various initiative names and will not allow you to spin up new initiatives even if the same/similar initiatives and all related assets have been deleted. My spidey sense is telling me there are a lot of components behind the scenes of Hub that we don't have access to through the UI (new and old).
I'll fire up some support tickets but maybe somebody here can help a brother out?
How are you renaming your initiative? If you do that in Hub (Settings panel) it should rename the groups and items associated with the site / initiative. The name restriction is on the groups which is what we check for uniqueness....so if you can remove the conflicting group you should be able to reclaim the name. I think the search for conflict names is fuzzier then we need it to be which we can look into.
...a similar story is true for deleting. If you remove things you need to make sure you get both the groups & the items and if you do that manually then the domain is left behind. Deleting is best done from the "..." in the site editor.
Thanks Graham Hudgins...I was on a call with support this morning, did a screen share which they recorded. They are going to work on the issue from the back end. I went through the steps with them (renamed contents, groups, etc...) and they confirmed I had done everything "correctly" but that the name was persisting behind the scenes. I've created a new initiative with a name that works for now so that I can continue moving forward. Support will follow up with me on this renaming issue...and possibly document it as a bug.