Notsure, that rockchip-multimedia-config package was strictly required to enable GPU hardware acceleration, nonetheless I installed it alongside with mali-g610-firmware, that was indeed required.
I was thinking to create a new topic, however this one fully matches my question and the problem I have. It turned out, that my previous comment on this thread was ahead of time - GPU hardware acceleration still does not work on DietPi/Bookworm with Orange Pi 5 (RK3588 chip). I used this method for verification in Kodi: [GUIDE] Kodi on Orange Pi 5 with GPU Hardware Acceleration and HDMI Audio - Orange Pi 5 / 5B / 5 Plus - Armbian Community Forums
In fact I can confirm, that this procedure works - shared and explained by the owner and maintainer of ppa:liujianfeng1994 - JianFeng Liu - aka @amazingfate. The problem though, I managed to get a fully working HW accelerated video stream with RK3588 (up to 4K@60fps) only using Armbian Jammy image - yes, it works indeed very well. But I failed to achieve the same result with DietPi/Debian/Armbian Bookworm OS - I failed to install/update required packages from Ubuntu PPA into Debian. Required steps are explained pretty well by the PPA maintainer/developer:
I decided to revisit this problem. Not having a better solution I rebuilt required packages from sources. Luckily Debian community made the whole build process quite an easy journey even for novices, when it comes to building the package from PPA: CreatePackageFromPPA - Debian Wiki
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