For posterity: No need for deligates as Ville Nurmi has pointed out here:
https://forums.unrealengine.com/deve…ontent-browser
Can just
TArray<FString> Folders;
FContentBrowserModule& ContentBrowserModule = FModuleManager::LoadModuleChecked<FContentBrowserModule>("ContentBrowser");
IContentBrowserSingleton& ContentBrowserSingleton = ContentBrowserModule.Get();
ContentBrowserSingleton.[GetSelectedFolders](https://docs.unrealengine.com/en-US/API/Editor/ContentBrowser/IContentBrowserSingleton/GetSelectedFolders/index.html)(Folders);