: Perhaps the most well-known custom ROM, LineageOS offers a clean, near-stock Android experience. It's known for its stability and performance enhancements. For the J400F, LineageOS provides a way to experience Android versions not officially supported by the device, often with performance and battery life improvements.
Give your aging Samsung Galaxy J4 (SM-J400F) a second life with a custom ROM. While official updates stopped years ago, the developer community continues to provide lightweight, high-performance software that can speed up your device and offer newer Android features. Why Install a Custom ROM on is an entry-level device with 2GB of RAM and an Exynos 7570 chipset j400f custom rom
I can provide a more detailed step-by-step guide once I know your specific goals! : Perhaps the most well-known custom ROM, LineageOS