I mean, I don't know if there's a way to support this on Chess.com. Checkers is basically such a variant, which arguably demonstrates why such variants have problems. Checkers requires an obscene material advantage to actually force a win. The reason that Chaturanga can sort of get away with its king baring rule is that it's rare to end up with your opponent having rooks and you not in the endgame but you're winning, and systematically capturing all the opponent's pawns, Ferzes, Alfils, and Knights isn't that difficult, and you can always fork or pin them against the king.
As soon as you start having the potential for the losing player to have nothing weaker than a rook to be checkmated, things get really out of hand. Rookmate is pretty drawish. Queenmate is basically impossible if your opponent is sentient.
Is there some way of creating a variant without any royal pieces, e.g., you need to capture all of your opponent's pieces to win?