Android phone manufacturers typically stop supporting their devices after 3-5 years. This means that, for example, the original Pixel is past its expiration date which means that the Android 13 update will never officially arrive on the phone.
However, developer Husson Pierre-Hugues got the update to work on the original Pixel phone. This is thanks to Google’s Project Treble framework, which has allowed Pierre-Hugues to load Android 13 onto the phone.
It’s far from a perfect upgrade because certain features don’t work, like cellular connectivity, but others do, like WiFi, GPS, fingerprint sensor, etc.
Unfortunately, if you were thinking of resurrecting your Pixel to install Android 13, it won’t be that easy. This is because in order to use Project Treble, you’ll need to have some programming skills and understand how updates are pushed through the framework, which means it’s not a method for the average user.