Why do older Android apps often keep working while Linux updates can break applications?

This isn't universal in either direction. Old Android apps can also break when Android changes permissions, security rules, hardware support, or removes compatibility features. On Linux, updates usually don't break applications when they come from the distribution's own repositories; problems are more common with abandoned software or manually installed packages. Without the distribution, version, application, and error message, it is difficult to identify a specific cause.

Linux has a much less uniform software stack. Applications can depend on particular versions of libraries, desktop components, tools, or services, and those pieces vary between distributions. An official package is usually rebuilt and tested when dependencies change, but an old standalone .deb, AppImage, or extracted archive may suddenly encounter missing or incompatible libraries after an update.

Android apps generally interact with the operating system through a standardized runtime and API. The system knows which Android version an app was designed for and can often provide compatibility behavior for older apps. As long as the app and runtime remain within a supported range, the app may continue working even after several system upgrades.

Formats such as Flatpak and, in some cases, AppImage reduce this problem by shipping more of an application's required runtime with the application itself. That can make newer software work on an older stable system, though it does not guarantee perfect compatibility. Android's tightly controlled platform gives applications a more consistent target than the many combinations found across Linux systems.