McBluna 
XMedia Recode is a free All-In-One audio converter, video converter and video editor.
XMedia Recode supports hardware accelerated video conversion from AMD, Nvidia and Intel.
XMedia Recode can convert almost all known audio and video formats, including AAC, AC3,Blu-ray, DVD, FLAC, H.264, H.265, Matroska (MKV), MP4, WebM, WMA and WMV.
XMedia Recode can only convert unprotected Blu-rays/DVDs.
https://www.xmedia-recode.de/en/
pronounced “screen copy“
This application mirrors Android devices (video and audio) connected via USB or over TCP/IP, and allows to control the device with the keyboard and the mouse of the computer. It does not require any root access. It works on Linux, Windows and macOS.
https://github.com/Genymobile/scrcpy
tinyMediaManager is a media management tool written in Java/Swing. It is written to provide metadata for the Kodi Media Center (formerly known as XBMC), MediaPortal and Plex media server. Due to the fact that it is written in Java, tinyMediaManager will run on Windows, Linux and macOS (and possible more OS).
https://www.tinymediamanager.org
Furthermore, it supports online database lookups from, e.g., Discogs, MusicBrainz or freedb, allowing you to automatically gather proper tags and download cover art for your music library.
You can rename files based on the tag information, replace characters or words in tags and filenames, import/export tag information, create playlists and more.
https://www.mp3tag.de
MediaInfo is a convenient unified display of the most relevant technical and tag data for video and audio files.
https://mediaarea.net/en/MediaInfo
MKVToolNix is a set of tools to create, alter and inspect Matroska files under Linux, other Unices and Windows.
https://mkvtoolnix.download/index.html
