It has been a while since we have heard about a CyanogenMod or AOSP ROM for Samsung Galaxy S6. Actually, there has never been a single AOSP ROM available for the Samsung Galaxy S6, unlike the Galaxy S5, S4 or S3.
The reason for not having an AOSP ROM on the Galaxy S6? It is simple – Exynos SoC. This time around Samsung decided to equip all Galaxy S6 handsets with its own Exynos ‘system on chip’. This was a new strategy compared to the Galaxy S5, which some devices came with Exynos and some came with Snapdragon.
While Exynos has been proven to deliver better performance than Snapdragon, developers prefer the latter for being more open source. Qualcomm releases updated sources for its Snapdragon SoC while Samsung does not. This makes it easier for developers to create AOSP ROMs for Snapdragon than Exynos.
After many months, developers have managed to boot the first AOSP ROM on the Samsung Galaxy S6. As seen on the video, the phone boots up to stock Android. Do not get very excited though. The AOSP ROM is based on Android 5.1.1 Lollipop and not 6.0 Marshmallow (CM13). Also, the build is still experimental and not available to the public.
You can check the source for updated news regarding the ROM. The work is far from over but hopefully the Galaxy S6 will have a fully working AOSP ROM in the future.