Orange pi 4 is based on rk3399
And rockchip integrates Mali T860 MP4 GPU
You need to know that mali gpu isn't open source
So, when you buy a Mali gpu device,
It doesn't support Linux at all
Only Android will run the acceleration
h265 it's part of the closed source drivers
When you want a device that run open source and GPU together please take something like adreno gpu
Don't use SBC for video editing,
If you want a video player, user interface,
Switch to Android... it's fast, and reliable.
Armbian on rockchip device is for server side of things.
For GPU Rendering on Linux instead of Android This is what you need
Hqnicolas's post in New to Armbian, veteran to Linux, but I could use a point in the right direction for my new Orange Pi 4 LTS (RK3399) for video acceleration in Kodi was marked as the answer