Everyone wants to install custom in their device because they are bored with the stock OS that comes with the device because the device manufacturers don’t promise to give OTA updates and Security Patches after some years. When time passes stock OS is going to slow because the device manufacturer gives lots of bloatware apps into the phone then there is no space for installing other apps.
So in this post, I will tell you how to download custom for any outdated device. In my case, I have my old phone Yuphoria which was launched in 2015. The last update given by the company was Android 6 Marshmallow.
So I will show you how to download the latest version of Android 9 Pie for my Yuphoria.
Method 1: XDA Developers
Search Device development XDA on Google

Here XDA forums and Developers pages are shown. Just visit those pages and search for the latest Android ROM.

Here I found the Android Pie ROM for the Yuphoria. Go to that thread and Download the ROM zip file.
Method 2: AndroidFileHost
Goto https://www.androidfilehost.com
AndroidFileHost is a website where you can find lots of stuff for Android Devices

Enter your device code name and search

After Downloading Zip file Download Gapps (Google Apps) according to your device architecture
Download Gapps from https://www.opengapps.org
Open Gapps is a website from where you can download Android 5 Lolipopo to Latest Android version Google Apps Package for custom ROMs.

That’s it. Using these methods you can easily find Latest ROM for your device and flash it into your phone.

