When a checksum is invalid, alert the user the phrase is not some thing produced by your app, and question whenever they would want to use it in any case. By doing this, your application only needs to maintain the wordlists for the supported languages, however, you can recover phrases https://ragingbookmarks.com/story19145376/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting