Balbes150, thanks for this information!
I am indeed really interested on having a functional debian/ubuntu rockpi 4 image working with VPU and GPU, because I am working in an educational project based on rockpi 4 to provide as cheap as possible minipcs for some schools. It is amazing all the information that you mentioned before and I am really happy to hear that finally this is possible from kernel 5.16.
Actually, yesterday I have been trying to put all the things that you mentioned here together, but I couldn't make them work. What I tried was this:
1. As rockpi 4 doesn't appear anymore as a mainly supported board in the arm downloads, I tried to compile from scratch (as I usually do). I Have chosen bleeding edge kernel with xfce on top of a Bullseye distro, because I supposed it was going to be the closest to the mainline kernel. It generated the image with kernel 5.15.19.
2. The image is working fine, but as I could check, no VPU or GPU was working.
3. I installed what you indicated about Kodi (probably missunderstood your indications here) and nothing extra happened, so I'm a little bit stuck here.
I have some questions at this point, because probably it is a better chance for me understanding all the packages that I should install to have it working and then generating u-boot from armbian and doing debootstrap by myself, adding exactly what I would need in the final image:
1. Which kernel version is needed (minimum) to make VPU working in mainline kernel with rockpi 4?
2. Are all the patches that you commented that were created for RK3399 included in the rockpi 4 kernel configuration?
3. Is it possible to compile with armbian's compile.sh script a 5.16 or 5.17 kernel?
4. Which are the software packages, kernel modules, etc needed to make VPU and GPU working? Is there any script/website where I can go to know more about this information?
Sorry for the long post, but as armbian forums don't allow more than 1 post per day, I had to condense the best I could all my doubts and problems.
Thanks again for your guidance on this guys! It is really helpful for me!