Are you thinking of a recruiter screen? I absolutely want to talk to the hiring manager for an hour, or more. This person will be my new boss, the more I know about them the better.
With the hiring manager? How they manage their team, how many people they manage, what does the team make-up look like, what does the day to day look like, how do they measure success, what are the traits they want someone in this position to have, is it easy to get time off, what challenges is the team facing, what are the opportunities for advancement, what's the worst thing about working there, or anything else that will help me understand both them and the team I'm coming in to. Also of course addressing any questions they have about me, since this is the person who will decide if they are offering me the job, and if they do and I accept, the person who will decide what I work on, have the most influence on raises, promotions etc.
Some of this is stuff that the actual engineers will give you a more accurate picture (ex what's the day to day like), but even for those things asking both the engineers and the manager and comparing them can give you an idea of how in touch the manager is with the realities of the team.