EF*CK Chat Keyboard

EF*CK is a free cross-platform open-source on-screen desktop emoji keyboard with a built-in text-filter-based emoji picker, Unicode text converter, and meme GIF search function ... Written in Python/Qt and extensible.

Upon activation, the app types your selection into the previously active (focused) window/input fields, such as a web browser or a desktop chat app, or similar. Supported platforms include Windows, macOS, and Linux (X11 and Wayland).