You can do this with yt-dlp and mpv: Just feed twitch url to mpv, pause the stream and let it cache (not sure if you'd have to adjust cache size, I have it set

You can do this with yt-dlp and mpv: Just feed twitch url to mpv, pause the stream and let it cache (not sure if you'd have to adjust cache size, I have it set to huge anyways), then adjust speed / skip anyway you want.