We don't know any good Letterly.app open-source alternatives yet.
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Alternatively, we recommend checking out LibHunt for open-source libraries and alternatives to Letterly.app.
Letterly has just launched and needs your support! It's a mobile app that converts any speech into clear & well-structured text using AI technology. Really useful for making structured notes, engaging social media content, concise meeting summaries, formal emails, and so much more.