Are these FFMpeg changes already in the last image on test.libreelec.tv or only on chewitt.libreelec.tv? Would you mind writing who is behind these changes, someone has taken it upon themselves to fix it, or maybe it's to your credit?
https://github.com/LibreELEC/LibreELEC.tv/pull/7387 was merged yesterday along with a few other things so the next round of images on the test server should contain the same content as the images on my share. The FFMpeg changes are by John Cox @ Raspberry Pi foundation. He is not working on Amlogic support, but we have common goals for v4l2_m2m support in FFMpeg and care that the current codebase that he is working on supports a range of SoCs and not just RPi boards. To further that I regularly test his experimental changes and provide feedback (especially when regressions are involved). In this case, a change made definitely helps with HEVC seeking. It's not a full fix though; that will almost certainly need changes to the kernel driver (which is lacking developers for aeons) but an improvement is still an improvement.