AMD setup missing HEVC/H262 hardware accelerated encoding/decoding

Har lesson learned. and expensive, sigh.

Thank you for the clarification, guess my oldest son just earned himself one hell of a gaming machine.

I already tried installing drivers only, without Adrenaline software on top, but that didn't help either.

It appears that you either relied solely on Microsoft Windows Update to update your GPU driver, or you installed the AMD driver improperly. My all-AMD system did show the hardware decoding and encoding checkboxes in the Media window, with the AMD option in the decoding section checked and grayed.

To fix that problem, please go directly to the AMD Web site, and download the latest driver for your RX 7900 XTX. Then, when you run the setup program, please choose the "Upgrade" installation option, and select either the "Minimal install" or the "Driver only" option in the drop box. The default "Full installation" option installs the gaming-enhancing features that actually interfere with the proper functioning of content creation programs.

My first video processing computer was built for me by a guy who was awesome at building gaming machines. All AMD. And ... tanked in Premiere.

I learned after that, to check what Premiere (and Resolve and AfterEffects) like, prior to ordering a machine. Expensive lesson. I used that for only three months before passing it onto the wife to use for her pro stills work. Sigh. And bought another new computer.

Breaks my heart, but got the answer I needed, thank you, appreciated.

Unfortunately, AMD does not make any hardware parts needed for "hardware acceleration" of long-GOP mp4 files ... at all. So that is why you don't have that available for long-GOP codecs.

Intel's H and K CPUs have the "QuickSync" hardware built in to them. Their F CPUs do not.

So for any hardware acceleration of H.264, you need a moderately recent Intel H or K CPU.

My desktop is built around a 3960x, with 24 fast cores. Which I need more than H.264 encoding. What H.264/5 I do, if there's enough it's a problem, I can proxy or transcode.

I did stick with an Nvidia GPU ... Premiere prefers CUDA, over anything AMD has.