Is there yet any hardware video decoding on Debian? If not Debian, is there something else that can do hardware decode with 4K MKV files as input?
Kodi currently shows GPU as llvmpipe, aka software rendering, which is too slow for 4K content 
No hardware video decode?
That is just your gpu where its not using the Mali for the UI.
Rkdec is the decoder but still some probs as search the forum.
Prob we are stuck on this Android hack BSP kernel 5.10.x …