The Idea list is not properly rendered if the user lacks the “Idea – Create” access. There is a view only profile that should only see ideas but not create.
We found that if you add the 'Ideas - Navigate' Access Right at the Global level for either the Resource or the Group along with 'Ideas - View', the Ideas page in the Modern UX will render correctly. This means that you can remove the 'Ideas - Create' Access Right and the user will be able to View but not Create Ideas in the Modern UX.