An unofficial build for Samsung Galaxy S3 i9300 (Exynos) has popped up online that give users of this 5 year old phone taste of latest Android – Android 9 Pie to be specific. Almost everything is working in this android pie ROM for Galaxy S3 except for video recording, ability to take screenshots, sensors and GPS. If you can live without them, this ROM is perfect to be used as daily driver.
To install it, you will need Galaxy S3 TWRP installed on your phone as that lets you install third party ROMs such as this one.
After that, download the android pie firmware for galaxy s3 from here and copy it to root directory of your Galaxy S3.
Boot into TWRP and flash the ROM from there.
The rom is much more fluid than Oreo, despite some other slowness in loading the configuration section. I have not had reboots, or sudden shutdown of applications.
All credits go to chronomonochrome for making lineageos for android.