This is an online tool that claims to estimate a player’s hidden matchmaking rating (MMR) in League of Legends. The tool requires the player to input their Summoner Name, select the region, indicate their current visible rank, and specify their LP gains per win. It then says it will analyse the last 30-50 games to estimate “actual MMR”, win rate, percentile, etc.

https://agatasmurf.com/mmr-checker/
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