Packages with the system-ffmpeg use flag

dev-qt / qtwebengine : Library for rendering dynamic web content in Qt5 C++ and QML applications

Use the system-wide media-video/ffmpeg instead of bundled.

dev-util / electron : Cross platform application development framework based on web technologies

Use system ffmpeg instead of the bundled one

games-emulation / ppsspp : A PSP emulator written in C++

Use the system-wide media-video/ffmpeg instead of bundled

media-libs / avidemux-core : Core libraries for simple video cutting, filtering and encoding tasks

Use the ffmpeg provided by the system.

media-tv / kodi : A free and open source media-player and entertainment hub

Use system ffmpeg instead of the bundled one

www-client / chromium : Open-source version of Google Chrome web browser

Use system ffmpeg instead of the bundled one