Little Golem
Little Golem is an application that allows you to play various board games online: Chess, Go, Hex, Amazons, Dvonn, Havannah, various word games, Tzaar, Lyngk, Four in Rows, Dots and Boxes, Conhex, Reversi, etc. More than 20 games and 100 variants of games.
There are several types of tournaments. Description is on https://docs.littlegolem.net