Anime/Manga Content ( Spanish)

There's a site called mangadex that has scanlations translated in many different languages, you can use the filter on advanced search to narrow it down to manga translated to Spanish (ES) or Spanish (Latam)

It's also quite a good way to learn foreign languages (open up chapters translated to English and other foreign languages and read them like a polyglot book)

Not so long ago I searched for a Spanish dub of a very popular anime and had a tough time finding active seeds on most sites listed on the Treasure Trove page.

I think YMMV depending on what you look for, and how old is it. I had much better results adding "Spanish" and "latino" to a simple google search. Turns out some people stream a single series on a website (as opposed to multiple series hosted on large streaming platforms).

Permanently Deleted

I've always went to animeflv.net, I haven't been there in a long time tho, so I don't know if the quality is the same.
For manga I've only consumed it in English, but tachiyomi has a lot of options for manga in several languages, you could check some of them.