9x10 Centaur

Pawn promotion at rank 9 (not 11) to one of the following pieces

Centaur (king+knight moves), called "general" on this website.

Archbishop (Bishop + knight)

Chancellor (Rook + knight)

Queen (Rook + Bishop)

No castling.

You win if you get stalemated.

The game was tested with Fairy Stockfish to confirm that it wouldn't be too unbalanced, win rate for white seems to be less than 50% when having the same strong engine play both sides.

Note that this variant currently has incorrect automatic draw rules due to chess.com being a bad site you should avoid.

There shouldn't be "draw from insufficient material" unless only 2 kings remain.

If only a single bishop or a single knight remains only the player without a piece should be able to claim automatic draw (since that is the only player who can still win by getting stalemated).

That is not a problem in terms of prolonging games much since you can force a draw pretty quickly (3-fold repetition) if you are the player with the piece left.

50-move rule for draw might not be ideal for this game (at least not regardless of material) since there are endgame that may last longer than that (such as queen & knight or queen & bishop vs centaur). I recommend using a 250-move rule (exceptions are allowed if they don't result in more draws with perfect play regardless of starting position).