Hi,
in a number of our installations (including a fresh installation), custom blocks on site level work in OJS 3.1.0-0, but not in OJS 3.1.0-1.
In 3.1.0-1, custom blocks can be created, but if they are added to the sidebar, both the whole sidebar and the footer are not shown anymore.
Besides, in all 3.1 installations, there are “add item” links (without function?) in the sidebar management, see image.