itch.io

Here are the rules for participating in this event:

    You must use the GDevelop game engine to make your game. The engine is free and open-source. You can find it on our official website.
    The games must not include offensive, discriminatory, or NSFW content of any kind. This is an event for anyone and everyone! So don’t be rude. 
    Harassment, harmful behavior, or offensive material toward players or other participants is not allowed. Admins may disqualify entries at any time without warning for violations.
    Games must be submitted through itch.io for rating as well as gd.games (see videos below for instructions).
    Games must be published to be played on browsers, without requiring extra hardware.
    Any text must be in English.
    You may team up! And we encourage it. You can find teammates on our Discord server. The maximum number of team members allowed is 4, and only one submission per person/team.
    The game itself must be made within the jam time period, and you may not submit any work or updates during the community voting period, nor during the judges' voting period. (Three days after community voting ends)
    You may use pre-made, publicly available, and purchased assets, as well as GDevelop's built-in asset library, or other assets you have the legal rights to use. Just remember to credit properly. 
    You can use pre-existing events and extensions. But do not write events specifically for this jam, ahead of time.

I'm in the same boat. Currently working on a little multiplayer proof of concept for the jam. What I'm doing to ensure that, despite it being multiplayer, it can be judged without requiring a player 2 is creating a "level 0" which doubles as a single player tutorial to show players the ropes and give them an idea of how it works. Maybe try creating a rudimentary state-machine that a single player can play against? 

Good luck with the game!