Kodi uses a 'compromise' but safe default for software deinterlacing. It's possible (with patching) to make it use other deinterlace algorithms that ffmpeg supports, but older ARM SoC boards like S905 don't have CPU grunt for the fancier ones that give better results. The S905 hardware has a dedicated deinterlace function, but software support for that only exists in the Amlogic vendor codebase that Kodi and LE moved away from. Older LE/CE images are more feature complete.
DRMPRIME is a zero-copy rendering path (nothing to do with Amazon); meaning we read the video stream and then all processing stages through Kodi, FFMpeg, and kernel drivers; exchange a pointer to the original data in memory instead of reading it from RAM, changing it in some way, then writing back to RAM again. It's more efficient, but it's use requires the kernel hardware decode drivers which are not perfect. The only alternative is to disable hardware decode and use ffmpeg software decode. Playback start and seek on HEVC media then works great, but unless the video bitrate is extremely low you won't have enough CPU grunt to handle 1080p media. If you only need to play SD or 720p media (or have faster hardware like S922X/A311D) it's an option though.
Nobody is working on the hardware decoders for several years now, so I have no expectations of improvements coming. For some users AMLGX works good-enough. For others not-good-enough. I am not a driver developer so I'm merely keeping the status-quo until either someone appears to do work, or the hardware dies out. S905 is now a decade old so the later is more likely.
