Rules: No delivering checkmate. That's the only rule. Win by flag, threat of flag (player with less time has no legal moves), or if you capture all of your opponents pieces.
I played around 30 games of this variant tonight with crimsonvortex, fuzzician, dunkirk1941, archdukeshrimp, seanyao1, and others.
We tried 2 versions. First, if a player has no pieces down on the board, they lose. Second, if a player has no pieces on the board, but some pieces in hand, they haven't lost but must immediately place down a piece. We preferred the second.
It's a very fun variant. We played with increment (and recommend this), but you don't need to. The games tend to be quite long. It's very chaotic and unintuitive, sometimes a game will be decided because one player who was winning accidentally drew the opponent's king into a mating net. Often we just accidentally delivered mate.
A few example games:
https://www.chess.com/game/live/12456987519
This game is instructive. When I as being attacked, I deliberately made my king unsafe so that CrimsonVortex, my opponent, couldn't continue to check me and capture material without mating me. (It turns out he could have continued with 29. Nxh8 30. Nxe6 instead. Still, N@f8 and B@h8 are thematic moves for this variant.)
https://www.chess.com/game/live/12459425951
Here is another instructive game. Crimson's move 73. @g4+!! is a brilliancy, as I have no legal moves other than checkmating Crimson. I made the mistake of drawing Crimson into a position where I have no checks that aren't mate and he capitalized perfectly.
https://www.chess.com/game/live/12463559953
I won this game because I set up a position where I was able to farm my opponent's pieces. From move 59, I set up what is essentially a windmill, and my opponent ran out of droppers to block with (and resigned).