A popular variant of go is “kill-all go”, where Black has a very large number of handicap stones, and White wins if they can make a living group.
If the handicap stones are already placed, then this variant can easily be played on any go server, for instance by using Chinese rules and setting a komi close to 361, so that White wins if they have at least one living group.
However, there is another variant with a kind of “auction” for the number of handicap stones at the beginning of the game.
In this variant, at the beginning of the game, both players play with black stones. This goes on until one player, instead of playing a black stone on their turn, says “I can kill you now”. Then, this player keeps the black stones; the other players becomes White. From this starting position, White plays first, and play alternates normally. White wins if they can make at least one living group.
This variant doesn’t seem particularly convenient to play on a standard go server. It might be well-suited for the server for variants.