FWIW just did a quick test with rmlint
and I would definitely not trust an automated tool to remove on my filesystem, as a user. If it's for a proper data filesystem, basically a database, sure, but otherwise there are plenty of legitimate duplication, e.g ./node_modules
, so the risk of breaking things is relatively high. IMHO it's better to learn why there are duplicates on case by case basis but again I don't know your specific use case so maybe it'd fit.
PS: I imagine it'd be good for a content library, e.g ebooks, ROMs, movies, etc.
fclones https://github.com/pkolaczk/fclones looks great but I didn't use it so can't vouch for it.