I've used Language Transfer with good success. Don't even need to sign up, you can just go, click on a course and start streaming lessons. You can also download them locally.
https://www.languagetransfer.org/free-courses-1
The idea is to create rules that help you "transfer" words from the source language into the target language, hence, "Language Transfer".
For example, going from English to Spanish: Words in English that end in ation, will end in acion in Spanish.
Confirmation -> Confirmación Conversation -> Conversación
Further, words following this rule are "ar" verbs. Confirmation -> Confirmación -> confirmar
Another one is words ending in al, which came to Spanish and English via Arabic... are the same. Just said with an accent.
Normal -> Normal Formal -> Formal
A few rules might get you a few hundred words. And while some words might be more formal than how something is typically said, you should still be understood.
They're completely donation based, ad-free, and no sign-up required.
I noticed I only got the rate limiting error when searching for an app on Aurora, but not to download and install. But how to get to the install page if you can't search?
I opened Firefox/Fennec on mobile, searched for an app, clicked the result for the Google Play store. Once on the play store page for the app was open, I would choose the "Open in App" option from the Firefox menu and select Aurora.
That would launch Aurora and bring me directly to the App Install page. From there I could complete the installation.
This was sometime in 2023, but hopefully it will still be helpful today.