Computer Configuration > Administrative Templates > Microsoft Edge > Startup, home page and new tab page
Both
HKLM\Software\Policies\Microsoft\Edge
By default, the Microsoft Edge new tab page includes three Bing Chat entry points: one inside the search box, one in the Bing autosuggest dropdown when users click or begin typing in the box, and one as a suggested prompt below the box. If you enable or don't configure this policy, these Bing Chat entry points continue to appear on the new tab page. If you disable this policy, all Bing Chat entry points are removed from the new tab page.