nVidia drivers now support MESA/GBM which can do HDR, but only through Wayland; which official LE doesn't use, and even if it's made to (with a self-built image) Wayland doesn't support dynamic refresh rate switching so the desktop refresh rate is fixed, e.g. 60Hz so you may find media playback has glitches and such as 23.976Hz or 25Hz content is adapted to that rate. Or you can use Xorg, but that doesn't support HDR at all. Oh, and Kodi only supports VDPAU not NVDEC.
I haven't used x86_64 hardware for a decade so I'm not going to recommend alternate GPUs (in part because vendors breed new stuff faster than I can keep up with it) but the general advice is: Intel = #1 choice, AMD = #2 choice, nVidia .. distant #3 choice.