Videomass is described as 'free, open source and cross-platform GUI for FFmpeg and youtube-dl' and is a Video Converter in the Video & Movies category. There are four alternatives to Videomass for a variety of platforms, including Windows, Linux, Mac, BSD and Windows S. The best alternative is HandBrake, which is both free and Open Source. Other great apps like Videomass are FFmpeg (Free, Open Source), VidCoder (Free, Open Source) and Shutter Encoder (Free, Open Source).
HandBrake is an open-source, multithreaded video transcoder – it compresses and converts digital media from one format to another. HandBrake can rip encrypted DVDs with libdvdcss (libdvdcss is installed with VLC media player on macOS, or AnyDVD/DVD 43 on Windows).
FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge.