p-menu no longer expanding on hover - after PrimeNg upgrade

[primelooc]

I've upgraded from PrimeNG 6.1 to 8.0 recently. I'm using a simple navigation menu:

<p-menubar [model]="menuItems">
</p-menubar>

- where menuItems is a simple array of MenuItems[] with their label and routerLink values set. Some of these have child menus, set up via the 'items' field.

In the earlier version of PrimeNG any top level menu items that had child items would automatically expand when the mouse hovered over them. In the newer version, this no longer happens - and I can't see an obvious way to re-enable this behaviour? Is this still possible?

Any help would be much appreciated!