Open Source C# Sound/Audio Software for Linux

FFmpeg Batch AV Converter is a free universal audio and video encoder for Windows and Linux (via Wine), that allows to use the full potential of ffmpeg command line with a few mouse clicks in a convenient GUI with drag and drop, progress information. Some fancy wizards make things easy for non-experts. Thanks to its multi-file encoding feature, it may be the fastest a/v batch encoder available, since it maximizes system resources usage by launching as many simultaneous processes up to user cpu thread count. You can change encoding priority, pause and resume, set automatic shutdown. It is good for seasoned ffmpeg users as well as beginners. It provides unlimited single or multi-file batch encoding for almost any audio/video format. You can use any set of parameters and try them before starting encoding. You can multiplex streams, subtitle videos (as track and hardcoded), trim, concatenate, record screen, multimedia info. Included youtube-dl / yt-dlp frontend GUI to download urls.

OnionMedia is a free video and audio file converter and downloader that works with ffmpeg and yt-dlp. It supports a huge amount of formats and codecs and is open source on GitHub.