Big Sur confirm alert button keyboard shortcut In Catalina and earlier versions of macOS, certain keyboard shortcuts worked for dismissing alerts, but these same shortcuts no longer work for me in Big Sur.
You could and you can still cancel alert dialogs via esc and alerts with a recommended action (highlighted in blue) you can dismiss them with enter.
But you could also trigger an alert's action with, for example, ⌘ command + D, based on the title of the button (presumably).
No such keyboard shortcut I try works on the new Big Sur alerts so far. Is there a working keyboard shortcut here?
The new destructive action doesn't have a keyboard shortcut by default. This is likely by design:

[it] allows the system to guard a destructive-action button against accidental presses

You can enable keyboard navigation for controls (previously called Full Keyboard Access) in System Preferences → Keyboard → Shortcuts → ‘Use keyboard navigation to move focus between controls’. With this option enabled, the Cancel button is focused for activation with Space, and you can Tab to the Delete button and activate that with Space too.