footer has been completely removed on version 12.3+ and will no longer render any contents from this layout and its component views.
It's redesigned replacement is in sidenav-bar, the last sidebar-nav-item-group metadata layout named sidebar-nav-item-group-bottom.
Note: sidebar-nav has different states that must be handled when refactoring your footer buttons as well as secondary actions (submenu).
Follow this throughout example to Move your Footer Content to Sidebar-Nav.