>
> With Emacs 28 when I type
>
> C-h f RET set-face-a RET
>
> I get a help window on ‘set-face-attribute’.  Now I'm asked to 
> [Confirm].  Kindly add some way to get the old behavior back.
>

I suggest

(define-key minibuffer-local-must-match-map (kbd "RET") #'minibuffer-force-complete-and-exit)