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uMatrix
Discontinued uMatrix: Point and click matrix to filter net requests according to source, destination and type
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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
Nearly everything is for safety, because uMatrix blocks things that have the potential of compromising privacy and/or security. However, there are certain things that websites require to work properly, so the trick is figuring out what to block and what to allow. You can learn about per-scope switches, including what blocking mixed content does, in the wiki and the pages it links to.
That site...doesn't sound like something I would want to visit. Something unrelated you could try is using youtube-dl to directly download the video to see if the videos you want are still there. Just install it and run the command yt-dlp https://YOUR_LINK_HERE.