Not websites, but here's this:
https://play.google.com/store/apps/details?id=com.opinoapp.opino_flutter
Nice, I use similarsites which has a Google Chrome extension you can click on any website and get you guessed it similar sites.
Also Alternative.to which is more for software.
While this allows you to pull PDF files from any sites where it's available, here's how I prefer to use it:
Got to PDFdrive.com or z-lib.org (or one of the other ebook sites in our wiki), and search for the book you want. Press on it, then press the download button ONCE. It will begin preparing the file. Then, when it's done, another download button will appear. Click and drag that icon over into the next tab, and drop on the area it says to drop it. Then, let the magic happen
idk but if it had to be one , it should be something like myanimelist.net , it does exactly what you want but it is only for anime/manga
note: https://simkl.com/ this is a site i found , its a good one , you shall try , and pls tell me your review of it , or update us if you find something better
Credit to u/OriginalHeartbreaker" I ADORE https://mynoise.net/ It's an archive of customizable sound generators with everything from music, nature sounds, sound cancelling, ambiances, and meditative drones etc. I focus best with some kind of white noise, and this website has a ton to choose from and it is free. My favorite feature is the customizable, animated sliders so you can listen to storms that ebb and grow automatically. It is great for TTRPGs too. The sound engineer who runs it has put together all kinds of specific settings like churches, cities, forests, faires, dungeons, etc. Seriously, people should check it out "