Samsung stopped churning out updates for the Galaxy Alpha android phone a while ago but XDA developers are busy at work and they are still pumping out quality ROMs that bring latest android 7 Nougat to the users. This one is called Lineage OS and it brings Android nougat onboard. It shall be noted that it works only with SM-G850W variant of Galaxy Alpha. This ROM does not work with Exynos variant (SM-G850F) nor a locked bootloader (SM-G850A). Here is how to flash it.
Make sure that your SM-G850W has the Lollipop bootloader and modem (The last installed stock ROM must be 5.0.2).
Flash Galaxy Alpha TWRP recovery via Odin.
Use Odin without ‘Auto Reboot’ option.
After flashing TWRP via Odin, reboot to TWRP recovery (Vol UP + Home + Power). Don’t reboot to the stock image which restores the stock recovery.
Boot to TWRP recovery (Vol UP + Home + Power).
Wipe data / Factory Reset
Install the ROM (CM zip).
Install the Gapps.
That is it – you are now running android 7 on your Galaxy Alpha. Again, this ROM is only compatible with Snapdragon version of Samsung galaxy alpha and not Exynos variant that is sold in many parts of Asia.