The best part of this technique is the software does not trim or re-encode the video, it just adds the .srt file to the video forever.
Here's the link to download the software used in the video to patch the subtitles to the videos
Click here:-
https://filehippo.com/download_mkvtoolnix_for_windows/
Download youtube subs
https://downsub.com/
Download youtube subs
https://downsub.com/