I run the Scrypted Add-On on an ODROID M1S, which has a Rockchip chipset. Scrypted provides a Rockchip Essentials plug-in that enables hardware accelerated ffmpeg. According to this blog, you need access to several /dev entries that HAOS does not expose. (The blog is for a different board but similar chipset.) We can see which entries need to be present in the Docker configuration section. It says to map the following entries:
"/dev/dri:/dev/dri",
"/dev/dma_heap:/dev/dma_heap",
"/dev/rga:/dev/rga",
"/dev/mpp_service:/dev/mpp_service",
3 of those are not exposed by HAOS. They’re not in the /dev tree at all.
If HAOS were to expose those /dev entries at the Linux level, we should be able to pass them through to Scrypted and setup Rockchip ffmpeg hardware acceleration in the plugin.