Studio UI is not able to load SiteAccess correctly when they are on another hostname. In this situation you would go to the Landing Page, select a site access and it would block the UI.
I think it is related to Sessions. Indeed on different hosts they would not be shared.
I have got a workaround, I am letting the URIElement matching on my configuration and then I block the direct URI access in Varnish.
But I should not have to do that.
That configuration works because of the URIElement:1, if you remove it, it fails the Studio UI.
But the workaround is not enough, I need to add a server side configuration
nova.group.dev/yuseofr would go on the yuseofr (which is wrong)