How to prevent users to download videos from lms website?

I found this answer online which responds your question

The problem that you are going to run into is a fundamental one about how videos on websites work. To watch a video, let's say on youtube, my browser starts downloading the video and shows it to me as it does (this is called streaming) by the time I have watched the entire video, I have also downloaded it. If my browser could not download the video, it would be unable to play it to me.

Every page, image, a and anything else you view in a web browser is downloaded before you can see it.

While there are ways to stop people from keeping a copy after watching a video, there are even more ways for users to get around that. After all, your server already sent them a copy of the video so they could watch it.

The best you can hope for is to make direct video file access very hard and use a streaming-based player without any file-based cache. A sufficiently motivated user will still be able to keep a copy and there is very little you can do about it.

You may be better off finding ways to add value to the viewing on your website experience so that users feel that they would miss out if they cached the video for offline viewing.