The Samsung Galaxy J400F is aging. Its hardware is fine, but its software is crippling it. By flashing a J400F custom ROM like LineageOS 20 or Project Elixir, you transform a laggy, storage-starved phone into a usable secondary device or even a daily driver for light users.

There is a solution that doesn't involve buying a new phone:

You lose Samsung Pay (irrelevant on a budget phone) and gain three more years of useful life.