But where do you source the files? I'm willing to pay for a deck, but it seems impossible to find good information without spending a ton of time researching it. Too much noise/signal ratio in this space.
Take a read on this: https://augmentingcognition.com/ltm.html
The author, among other topics, makes a case for the creation of personalized decks. That practice has been really valuable to me.
You're correct this is a problem. I paid for sprachenlernen24.de which is German to many languages and very good. Not sure about other source languages though.