The only vtt to txt conversion we know about is something like export of video subtitles from WebVTT format to plain text, although that might not be actually needed, since you can open .vtt files with any text editor.
But if you want to export just the text without the tags, this might actually require some parser or just professional video subtitle tool that can simply export the content. But we have no information about any specific utlity or solution designed just for vtt to txt conversion or similar.
Updated: August 29, 2023