You can become a software developer without a laptop or computer by using your smartphone.
Termux is a Linux-based terminal emulator on Android that allows you to do anything, including using it as an IDE.
Kiwi Browser is a useful tool for web developers as it allows inspecting website code, checking the console, and installing Chrome extensions on a mobile browser.
JStudio is a recommended app for Java developers, particularly for building Android apps, although it doesn't support the latest AndroidX features.