Apps to Extensible via Plugins

Geeqie is a blazingly fast and extremely customizable Gtk+ based image viewer designed for Unix-like operating systems. It excels at efficient photo browsing, organization, and basic editing, making it an ideal tool for photographers and anyone dealing with large image collections.

Angry IP Scanner is a free, open-source network scanner designed for speed and simplicity. It quickly scans IP addresses and ports across any range, making it an essential tool for network administrators and users needing to discover devices on their network.

Quod Libet is a highly extensible GTK+-based audio player for Linux, focusing on powerful music library management and flexible tagging. Written in Python and using the Mutagen library, it offers extensive customization and handles diverse audio formats seamlessly.