Go to the video you want to download, open the DevTools in your browser (F12 in Firefox), go to Network (you might need to reload the page), play the video. In the search bar under Network type in .m3u8. You'll get a file likely named master.m3u8. Right-click on it 'Copy value' than 'Copy url'. Paste this in the following yt-dlp command:

yt-dlp \
  --add-header "Referer: https://vidmoly.to/" \
  "https://paste-url-here.to/master.m3u8"

This should download the video.
If you want the subtitles, search for .vtt instead (you might need to select the desired subtitles in the player first). You can directly open the subtile file and download it.

I really hope someone can give you an easier solution.
Don't hesitate to ask further questions!

Some background

The the website is not supported and the generic downloader from yt-dlp doesn't work, hence the need for the m3u8 playlist. Their primary video host seems to be vidmoly, which I found that under the Request Headers.
BTW vidmoly as a standalone website is also not supported in yt-dlp with the hilarious reason:

This site looks like it is primarily used for piracy and therefore cannot be supported.

[–] dabaldeagul@feddit.nl 5 points 2 days ago

If you look through the FAQ section the reason for this makes a lot of sense, and is similar to what I would've expected.

The short answer is that supporting piracy sites would in all likelihood result in the project being shut down. In the past, other similar projects have been shut down due to supporting piracy sites. The yt-dlp maintainers are of the position that supporting such sites is not worth the risk.

[–] orvorn@slrpnk.net 6 points 2 days ago

Try jdownloader2.

[–] land@lemmy.ml 5 points 2 days ago (2 children)

Try this extension

https://www.downloadhelper.net/

[–] MissingInteger@lemm.ee 3 points 2 days ago (2 children)

I just tried it and this does work but you need to install their CoApp, which seems to basically just an ffmpeg wrapper.

[–] land@lemmy.ml 2 points 2 days ago (1 children)

It was a great experience until they started charging $19.99 for every additional item you download.

[–] MissingInteger@lemm.ee 4 points 2 days ago (1 children)

Yeah, just stumbled across that.
Video DownloadHelper a blast from the past. Haven't used that for more than a decade (I discovered youtube-dl and never looked back). I didn't look further in my testing, only promted me for a license when a wanted to download only audio, which seemed kinda scummy since there isn't even a pure audio source on the website as far as I can tell.

[–] land@lemmy.ml 3 points 2 days ago (1 children)

Does YouTube-dl works on all websites or just YouTube?

[–] MissingInteger@lemm.ee 4 points 2 days ago

yt-dlp (the most up-to-date version of youtube-dl) has hundreds of supported websites. The generic downloader can download from unsupported websites most of the time and if that doesn't work you just paste in the m3u8 file as seen in my answer.

[–] vimmiewimmie@lemm.ee 1 points 2 days ago (1 children)

It should allow you to copy the media URL in the free version of the extension, then just paste into yt-dlp, if that all works for your needs.

[–] MissingInteger@lemm.ee 1 points 2 days ago

That sometimes works, but you might need to add some arguments like here --add-header "Referer: https://vidmoly.to/"

[–] orize@lemmy.dbzer0.com 2 points 2 days ago (1 children)

That's what I found and am struggling with RIGHT NOW! It seems that If I had Firefox it would work straight away. But I run Waterfox, and it doesn't work. Trying to figure out where to move the install files into Waterfox... Hmmm...

[–] MissingInteger@lemm.ee 2 points 2 days ago

According to the waterfox documentation you should just be able to install the extension from addons.mozilla.

If you want to use this addon on this website you still need the CoApp installed separately.

[–] wizardbeard@lemmy.dbzer0.com 3 points 2 days ago

Have you tried tossing the URLs into yt-dlp? That's the go-to software for downloading video from streaming sites.

[–] airman@infosec.pub 3 points 2 days ago

Did you try yt-dlp? It might work.