batch scan playlists for dead entries

It's probably also not exactly what you are looking for but you could

• install the freeware audio player foobar2000 in portable mode,
• then open your m3u8 files with it and then
• choose from the menu Edit -> Remove dead items.

foobar2000 imports the m3u8 to a playlist and the 'Remove dead items' command removes all missing files from it, which are also listed in foobar's console [menu: View]. The console's content can be copied or written to a file.

In addition you could try the component foo_playlist_revive in order to adjust links to missing files automatically if possible.

Finally export foobar2000's updated playlist back to m3u8.