MissingInteger

Both btdig and nyaa.si are online and fully operational, that seems to be a proplem on your end.
Skullxdcc background image does not irritate me because the background of the search results is black and not transparent.
Here is a more robust filter to block the background image:

skullxdcc.com##.fake-body { background-image: none !important; }

Interesting collection.
Some notes:

• There are two nyaa proxies pages listed. nyaa.si is the actual "official" one. There has been malware in the past on nyaa proxies.
• sunxdcc is being fazed out. The same developer made a new search engine skullxdcc.com
• btdig.com is another highly capable dht crawler that could be added to the "Torrent Site" section.
• Kickass torrents is long, long dead the remaining sites are sketchy copy cats.
• kinozal requires sign-up; would probably good to note in the right hand column.
• irc.undernet.org/bookz and irc.irchighway.net/ebooks are XDCC servers for ebooks
• I don't know if this would fit the DDL sites category, but some phenomenal ebook sites are: annas-archive.org, libgen.is, libgen.li and z-library.sk

It's also an odd choice to put the predbs at the top, since that's probably the category that people are least interested in, in my estimation.

The fmhy.net website is far better to navigate.
For Asian content maybe checkout the non-english section.

This one is open source.
Adguard is an massive contributor in the adblock scene.
Many of their products are free (Adguard Home, DNS, etc.). Even this one has a free version. They want to make money as a company and on iOS you gotta pay the Apple tax.

But you can install Adblock extensions (but only in Safari)!
The best by far is Adguard.

Do you use the paid version of Adguard?
For me on iOS it's almost as good as uBO on Firefox.
No blank spaces where ads go, support for every filterlist I want, especially nice for blocking cookie notices.

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.

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

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.

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.

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

Okay, this was harder than anticipated. Maybe someone can find an easier solution:

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!