Do you know any website for organising online chess tournaments with swiss pairing method ? I know lichess.org but they don't support it anymore :/
The related question How to organize a chess tournament appears to have several suggestions; I'm not personally familiar with any of them, but most of the links seem to still be active.
You can do it on playchess.com in the 'tournaments room'.
You can try chess.com, but you must be a premium user to create a tournament.