I have tried out the user interface of Lingua Libre, and I love the project!
The step where I get stuck most, is the third one in the recording wizard ("Details"). As a casual passer-by who wants to do useful things but does not know where to start, I am confused and don't know which words to type/choose.
Maybe it's a good idea to make a good bunch of pre-selected lists of words to pronounce, for clueless and aimless people like me... Perhaps you can investigate which words are most often used in each language and/or typically first learned in a new language, and also make pre-selected list of e.g. food items, everyday household items, everyday items outside and in cities, related to work, school, travel, etc etc etc.
If you base these on Wikidata items, they can perhaps appear in the language that the speaker selects? Not sure if this will work in 100% of cases.
I hope this suggestion is useful!