This reply won't be very helpful, but I came here to say that I've seen the same thing. I did *not* have Handbrake QSV installed/working previously, but I just built an Alder Lake i9-based system and can't seem to get GPU encoding working no matter what I do. I've spent hours researching on these forums and tried everything -- different versions of device additions into Docker (/dev/dri, etc.), 'lowpower=0' switches in Handbrake...and nothing seems to work. I should state that I'm still on 6.12.14.
Like CelestialTeaPot, I too do not see Handbrake as an app icon in Active Apps (though I do see my Frigate icon consistently...which I should). Any thoughts or help would be most appreciated!