Intel were the source of the initial HDR support in the kernel, and Team Kodi helped them to get code merged. Over time lots of ARM SoC devices then added support for the required DRM/KMS plumbing too. Substantial Allwinner support and a moderate amount of Rockchip support for media codecs and DRM has been developed or refined by our staff developers, or in collaboration (behind the scenes) with professional developers working on Linux media support (folks from Collabora, etc.). Over time we've accumulated many of the main V4L2 'name' developers into our Slack instance; we support a broad range of V4L2 using hardware and we have a staff with lots of test devices, test media, and experience of spotting and intelligently reporting quirks in media performance and playback - so we gain from their efforts, and they gain from our testing and inputs. RPi Foundation has an excellent team of in-house staff working on firmware and kernel drivers, and both LE and Team Kodi have a long history of working closely with them to ensure RPi has great media support. Their support to us is the A1++ benchmark that other vendors are measured against (none come close). The RPi foundation's approach to RPi4 has been different to older devices; mainly as lots has been learned since 2012, but LE/Kodi have been instrumental in forcing them to drop proprietary codecs and embrace the GBM/V4L2 world and push everything "upstream" to benefit more distros and the wider Linux community. It's taken time to get things into decent shape, and while RPi4 is not perfect (not all codecs supported, etc.) it's still the best performing device for the average LE user to play with. Enjoy 
