Xabe.FFmpeg allows to download m3u8 playlist:

string output = Path.ChangeExtension(Path.GetTempFileName(), "mp4");

var conversion = await FFmpeg.Conversions.FromSnippet.SaveM3U8Stream(uri, output, TimeSpan.FromSeconds(1))
await conversion.Start();

/// <summary>
///     Save M3U8 stream
/// </summary>
/// <param name="uri">Uri to stream</param>
/// <param name="outputPath">Output path</param>
/// <param name="duration">Duration of stream</param>
/// <returns>Conversion result</returns>
Task<IConversion> SaveM3U8Stream(Uri uri, string outputPath, TimeSpan? duration = null);