How can I update my S5?

[Johnwhite5823]

Hello, I know this is an old phone but I wanted to try updating it. So if anybody can help, I would strongly appreciate it.
I have an unlocked Galaxy S5 that I purchased from Amazon. It's an AT&T branded phone but I am using T-Mobile through a SIM card.
In "About device", it says it is a SM-G900A and it is running Kitkat 4.4.2. It also says it is "Kernel version".
I'm not really sure what this means but it would be helpful if someone guided me update it to the newest possible Android version.

 

[Thacy]

AFAIK, there is at least a Marshmallow version for SM-G900A.
Do you use Smart Switch or Kies on your PC? You may update your phone with them. Connect your S5 to PC and run the software. If there is any update for your phone, it will pop up a small window. Make a backup first.

You can also download Android 6.0 ROM for SM-G900A and flash it through Odin, but this is complicated and risky if you are not familiar with it.

Try Smart Switch or Kies first and see what happens.

 

[Johnwhite5823]

Smart Switch doesn't mention that there is a new update available and Kies states that it already has the latest firmware.
Is there a reason why there appears to be no further updates?
I'm willing to flash it if I have to. Where can I download the ROM that's specifically for my device?

 

[Thacy]

Look through this guide:
https://forum.xda-developers.com/att-galaxy-s5/general/galaxy-s5-android-version-6-0-1-t3419016

Make sure to download the right ROM according to your phone Build number and Baseband version.

 

[Johnwhite5823]

Thanks so much!
I followed the steps for "From Any Version" and followed the Odin method. As described, my phone was wiped but I saved it all beforehand on Smart Switch. Everything went really smooth.
Thanks for everything, feels a lot better not to be stuck on Kitkat.