For the past several weeks various Samsung Galaxy S5 models kept joining the Android 6 Marshmallow camp, and last time the aforementioned device reached our headlines thanks to Marshmallow-related news was yesterday, shortly after T-Mobile began the official Android 6 rollout. However, owners of the Samsung Galaxy S5 and customers of Sprint, US Cellular, or Vodafone now have an alternative, non-conventional route for acquiring Marshmallow on their devices. They can turn their attention to Cyanogen and the company's new "nightly" CyanogenMod 13 builds for the aforementioned Samsung Galaxy S5 carrier variants.
Custom ROMs are quite a wonder for smartphone users who want to have more control over their devices, and sometimes they can also breathe new life into older models who may no longer be officially supported with new software updates. CyanogenMod is one of the most prolific custom ROM names, and over the years, the team formed Cyanogen Inc which became a partner for several smartphone makers, all thanks to the creation of Cyanogen OS. However, the open-source CyanogenMod is still alive and kicking, and recently the CyanogenMod team released the first "nightly" CyanogenMod 13 builds for the Samsung Galaxy S5 at Sprint, US Cellular, and Vodafone. Now, while CyanogenMod 13 is based on Android 6 Marshmallow, nightly builds are not meant for day-to-day use, and some nightly releases are more unstable than others. On the bright side, nightly builds are regularly updated (usually on a daily basis) with new bugfixes and additions, and this allows curious smartphone owners to be more involved in the ROM's development.
Keep in mind that installing a custom ROM is generally not a user-friendly endeavor, and there are certain prerequisites that need to be met, including having root access and a custom recovery tool installed on the phone. Installation steps have to be followed to the letter, and there's always a risk of bricking your smartphone in the process. In other words, if you are not confident in applying custom ROMs and you don't feel like starting now, then you may want to wait for the official Android 6 Marshmallow rollout instead, if it hasn't reached your terminal already. Otherwise, several CyanogenMod 13 nightly builds for the Samsung Galaxy S5 at Sprint, US Cellular, and Vodafone, are already available for download from the custom ROM maker's website.