I don’t think I’ve shared this already: I made a language detection script to auto fill up the Language metadata field.
It uses https://dandelion.eu/ , you need to create an account and get a token, and replace “TOKEN” in the script with the token value. that means it sends your items data to this third party service, use it with care.
You also need to activate the Language custom metadata in Settings.
Then simply select a few items and let the script run on them.