Samsung most probably won't be upgrading your Samsung Galaxy S4 to Android 6.0 or 6.0.1 Marshmallow. At this point third party developers are making efforts to find a solution. In this article we'll go through some of the methods that would help users to update their device, irrespective of device maker's official Android support. The first of option is the widely adopted - CyanogenMod 13. The second option is also a kind of advanced ROM flashing scenario. The final way to upgrade the Galaxy S4 is mostly a virtual solution.
CyanogenMod downloads section has listed a bunch of collection of CyanogenMod 13 OS builds for all of the Samsung Galaxy S4 variants released till now. In case you are confused about the files available for this update, don't try to flash them to your device.
While the solution listed above utilizes CyanogenMod's special look at Android OS, the next solution is based on AOSP, the Android Open Source Project, and it is an elementary version of the new Android. It is named as AICP and lets you upgrade to Android 6.0.1 Marshmallow in Samsung Galaxy S4
Last solution is the Google Now Launcher. This launcher completely replaces the Samsung launcher, which was in-built in the smartphone.
Given below are the inclusions in the new Google Launcher:
• Vertical and faster scrolling of A-Z apps list
• One place to search for apps installed in the device and new ones on the Play Store right from the A-Z list.
• App Suggestions utilizes on-device intelligence to show the apps you're searching for in the top of the list.
• Enlarged folders which can have more than one page.
• Newly added Android Marshmallow Wallpapers.